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Kyiv Workshop (CoE 6842) Monitoring of Radio Frequency Spectrum New Communications Technologies & Implications on Spectrum Monitoring Professor Anastasios D Papatsoris Department of Informatics & Communications Serres Institute of Education & Technology [email protected], Tel: +30 23210 49157 http://www.teiser.gr/icd/staff/papatsoris/index_en.html Talk structure The aim of this talk is: – To review in a synoptic way the latest developments in modern digital communications techniques, – To present in a concise and illustrative way some of the dominant communications applications, and – To discuss the implications on Spectrum Monitoring from a technical and administrative point of view. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 2 New communications technologies The advances in technology have enabled the incorporation of complex digital communications techniques (modulation, coding, access schemes) in all radio communications applications in an economical way. This led to the so called “digital explosion” and most services and applications are today digital or about to become. Especially relevant to Spectrum Monitoring is the development of new modulation and access techniques, in particular OFDM and CDMA, respectively. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 3 COFDM COFDM involves modulating the data onto a large number of carriers using the FDM technique. The key features which make it work, in a manner that is so well suited to terrestrial channels, include: – orthogonality (the “O” of COFDM); – the addition of a guard interval; – the use of error coding (the “C” of COFDM), interleaving and channel-state information (CSI). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 4 COFDM – FDM If coping with any appreciable level of delayed signals is required, the symbol rate must be reduced sufficiently so that the total delay spread (between the first and last received paths) is only a modest fraction of the symbol period. The information that can be carried by a single carrier is thus limited in the presence of multipath. If one carrier cannot carry the information rate required, why not divide the high-rate data into many low-rate parallel streams, each conveyed by its own carrier – of which there are a large number. This is a form of FDM. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 5 COFDM – Orthogonality The use of a very large number of carriers implies that an equally great number of modulators/demodulators and filters, as well as an increase of bandwidth would be required to accommodate them. Fortunately, this isn’t the case if we specify that the carriers are evenly spaced by precisely fu=1/Tu, where Tu is the period (the “useful” or “active” symbol period) over which the receiver integrates the demodulated signal. This is in fact the equivalent of orthogonality in mathematics. k (t ) e jku t 1 – 4 June 2004, Kyiv 0, k j , and k (t ) (t ) dt 1, k j * j New Communications Technologies & Implications on Spectrum Monitoring © ADP 6 Preserving orthogonality In practice, the carriers are modulated by complex numbers which change from symbol to symbol. If the integration period spans two symbols, not only will there be same-carrier ISI, but in addition there will be intercarrier interference (ICI) as well. This happens because the beat tones from other carriers may no longer integrate to zero if they change in phase and/or amplitude during the period. This can be avoided by adding a guard interval, which ensures that all the information integrated comes from the same symbol and appears constant during it. The guard interval length is chosen to match the level of multipath expected. It must not form too large a fraction of Tu , otherwise too much spectral efficiency will be sacrificed. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 7 Use of IFFT and FFT In OFDM modulators, demodulators and integrators are realised through the exploitation of the properties of the discrete Fourier and Inverse Fourier transforms. In the transmitter, the modulated waveform is constructed though the application of the IFFT, whereas in the receiver the demodulation process is realised through the application of FFT. Common versions of the FFT operate on a group of time samples (corresponding to the samples taken in the integration period) and deliver the same number of frequency coefficients. These correspond to the data demodulated from the many carriers. Thus, the availability of cheap FFT ICs eliminated the need for thousands of modulators and demodulators. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 8 Choice of basic modulation At the receiver, the corresponding demodulated value (the frequency coefficient from the receiver FFT) has been multiplied by an arbitrary complex number (the response of the channel at the carrier frequency). The constellation is thus rotated and changed in size. How can we then determine which constellation point was sent? One simple way is to use differential demodulation, such as the DQPSK used in DAB. Information is carried by the change of phase from one symbol to the next. As long as the channel changes slowly enough, its response does not matter. Using such a differential (rather than a coherent) demodulation process causes some loss in thermal noise performance – but DAB is nevertheless a very rugged system. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 9 Choice of basic modulation When higher capacity is needed, coherent demodulation is preferred. In this, the response of the channel for each carrier is somehow determined, and the received constellation is appropriately equalized before determining which constellation point was transmitted. To do this in DVB-T, some pilot information is transmitted (so-called scattered pilots) so that, in some symbols on some carriers, known information is transmitted from which a sub-sampled version of the frequency response is measured. This is then interpolated, using a 1-D or 2-D filter, to fill in the unknown gaps, and is used to equalize all the constellations which carry data. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 10 Error coding Uncoded OFDM does not perform very well in a frequency selective channel. Thus, a soft-decision Viterbi decoder is used in the receiver. The Viterbi decoder adds logarithmic likelihoods to accumulate the likelihood of each possible sequence sent by the transmitter. The Viterbi’s soft decision thresholds are dynamically affected by the channel-state information (CSI), i.e., data conveyed by carriers having a high SNR are a priori more reliable than those conveyed by carriers having a low SNR. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 11 Interleaving If the relative delay of the echo is rather shorter than we have just considered, then the notches in the channel’s frequency response will be broader, affecting many adjacent carriers. This means that the coded data we transmit should not simply be assigned to the OFDM carriers in a sequential order, since at the receiver this would cause the Viterbi soft-decision decoder to be fed with clusters of unreliable bits. This is known to cause a serious loss of performance, which can be avoided by interleaving the coded data before assigning them to OFDM carriers at the modulator. Interleaving can be implemented both in the time or frequency domain. For a slowly varying channel frequency interleaving is appropriate, whereas in cases where the frequency response of the channel varies appreciably with time (i.e., large Doppler shifts), time interleaving is appropriate. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 12 CDMA Traditionally Code Division Multiple Access (CDMA) systems have been used almost exclusively by the military as a means of operating covert radio communications in the presence of high levels of interference. In recent years, the interference immunity of CDMA for multiuser communications, together with its very good spectral efficiency characteristics, has been seen to offer distinct advantages for public cellular-type communications. There are two very distinct types of CDMA system, classified as direct sequence CDMA (DSSS) and frequency hopping CDMA (FHSS). Both of these systems involve transmission bandwidths that are many times that required by an individual user, with the energy of each user's signal spread with time throughout this wide channel. Consequently these techniques are often referred to as spread spectrum systems. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 13 Frequency hopping CDMA Frequency hopping involves taking the narrow bandpass signals for individual users and constantly changing their positions in frequency with time. In a frequency selective fading environment, the benefit of changing frequency like this is to ensure that any one user's signal will not remain within a fade for any prolonged period of time. Clearly for frequency hopping to be effective, the users must hop over a bandwidth significantly wider than notch caused by frequency selective fading. In order to ensure that individual users never (or rarely) hop onto the same frequency slot at the same time, causing mutual interference, the carrier frequencies are assigned according to a predetermined sequence or code. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 14 Example of FHSS The GSM System has also provision within the Standard to change frequency on a frame-by-frame basis, making it a modest rate (1 / 4.165ms = 240 hops/second) frequency hopping CDMA system. The motivation for adding the extra complexity of hopping to GSM is twofold. – Firstly, the 200 kHz channel bandwidth of GSM is not sufficient to ensure that it will always be significantly wider than the coherence bandwidth of the multipath environment, and thus not corrupted by narrowband fading. – Secondly, if there is a strong interference source on any given channel, the hopping process will ensure that frames are only corrupted on an occasional basis. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 15 FHSS and SMon The FHSS signal parameters of interest include: full hop bandwidth; underlying signal modulation; minimum frequency difference between hops; instantaneous received power; hop rate and hop phase; angle of arrival (DF). When multiple FHSS signals are present in the same band, advanced digital signal processing (DSP) algorithms are required that identify and isolate the signals by hop rate, hop duration, hop phase, and angle of arrival since all of the signals will appear to be co-channel interference. FIGURE 10. Waterfall Plot of FHSS Signal 600 400 200 0 1 – 4 June 2004, Kyiv 0 10 20 30 40 Frequency New Communications Technologies & Implications on Spectrum Monitoring © ADP 50 60 70 16 Direct sequence CDMA In DS-CDMA, the narrowband signals from individual users are spread continuously and thinly over a wide bandwidth using a spreading sequence. By mixing the narrowband user data signal with a locally generated well-defined wideband signal, the user energy is spread to occupy roughly the same bandwidth as the wideband source. The wideband spreading signal is generated using a pseudo-random sequence generator clocked at a very high rate (termed the chipping rate). De-spreading of the signal is necessary in the receiver in order to recover the narrowband user data modulation and this is accomplished by mixing the received signal with an identical, accurately timed pseudo-random sequence. This correlation process has the effect of reversing the spreading action in the transmitter. De-spreading will only occur, however, if the correct sequence is used at both ends of the link, and if the two sequences are time aligned. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 17 DS-CDMA schematic 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 18 Multi-user performance Multi-user operation is achieved in direct sequence CDMA by assigning each user a different spreading code or a different time alignment of a common spreading code. Only that portion of the wideband spectral energy that has been spread by the same code as used in the receiver will be detected. Users are thus able to coexist in the same bandwidth and time space on the channel. Like frequency hopping, spread spectrum CDMA overcomes the problem of frequency selective fading by ensuring that most of the spread signal energy falls outside the fading 'notches'. If there is some correlation between spreading codes, as is almost always the case, then there will be a small contribution to any individual de-spread user signal from all the other spread users on the channel. Ultimately this puts an upper limit on the number of users that can co-locate on the same piece of spectrum before the unwanted de-spread energy gives rise to unacceptable data errors. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 19 DSSS and SMon The main parameters to measure for DSSS signals include: carrier frequency; transmitted bandwidth; number of users in the band; chip rate; modulation type; instantaneous received power; angle of arrival (DF). Since DSSS signals will appear to be wideband noise to conventional receiving and direction-finding equipment, new equipment and techniques are required in order to detect, process, and locate these signals. The preferred technique is to use a phase coherent multichannel (two or more) wide-band acquisition digital signal processing system. In order to demodulate the DSSS signal, the receiver must possess the same frequency, chip rate and spreading sequence as the transmitter, and it must be able to synchronize correctly to this sequence. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 20 Radio communications applications Fixed wireless access – LMDS, MMDS, MVDS Satellite networks VSAT star and meshed configurations High Altitude Platforms (HAPs) Digital Radio – DAB-T, DAB-S Digital Interactive Television – Terrestrial DVB-T/C, DVB-X (land mobile), Satellite DVB-S Mobile communications – UMTS – TETRA Fixed limited mobility – Bluetooth – HIPERLAN 1/2, HIPERACCESS, HIPERLINK 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 21 Network & system architecture Communication networks could be considered as divided into two parts: the access network and the core network. – The access network delivers the communication service to the end user whereas, – the core network (or backbone) transports high volumes of traffic between routers. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 22 Fixed Wireless Access (FWA) FWA: The provision of two-way broadband services through fixed microwave links. According to the frequency band of operation and the offered services the following technologies can be distinguished: – LMDS (3.4 - 3.6 GHz, 24 28GHz, voice, data, ΙΡ), – MVDS (40 GHz, video) 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 23 FWA network architecture An LMDS network consists primarily of four parts: network operations centre, fibre or microwave based infrastructure, base station and CPE. Various network architectures are possible within LMDS, MMDS, MVDS system design. The majority of system operators use point-to-multipoint wireless access designs, although point-to-point systems and TV distribution systems can be provided within the LMDS system. Both ATM and IP transport methodologies can be implemented by system operators at national level. Access protocols include both TDD and FDD schemes. Modulation can be dynamic according to channel conditions, and includes QPSK, 16-QAM and 64-QAM. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 24 Satellite network topologies Depending on the type of payload, basic reference architectures for point-to-point broadband can be considered: – Distributed bent-pipe satellite Internet access – Meshed regenerative satellite network for professional users or for backbone connectivity. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 25 Distributed bent-pipe satellite access Distributed broadband access via satellite provides a high-capacity point-to-point on top of multicasting for ubiquitous internet access. This architecture has a multi-star topology with few gateways that transmit one or more high data rate forward link to a large number of small user terminals. In the return direction, the remote user terminals transmit in bursts at low to medium data rates to the gateway. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 26 Meshed regenerative satellite network With on-board processing and switching topologies, the satellite is the focal point of a star network instead of a gateway earth station. The satellite is connected to the terrestrial gateways by high data rate links. On-board the satellite the onboard processor (OBP) demodulates and demultiplexes the uplink transmissions from user terminals and switches it into downlinks streams intended for particular geographical areas. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 27 Star TDM/TDMA VSAT configuration The Hub transmits an outbound channel (□) divided into time slots (TDM), which is received by all VSATs, but can be addressed to a group. Each VSAT contends for time slots on a shared TDMA inbound channel (□□□). If they collide in a slot, they re-transmit after a random time delay. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 28 SCPC mesh/DAMA system A VSAT uses a TDMA CSC (command, signalling & control) (□) channel to request that the Master station sets up a link between the requesting VSAT and another. The Master station then informs the called VSAT on request and allocates two channels (□□) to serve as bi-directional link between the two sites. As soon as the call is finished, the channels are returned to the pool of available capacity. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 29 VSAT equipment The VSAT consists of two units – one outdoor and one indoor. The outdoor unit comprises of an antenna of small dimensions and a microwave transceiver. The indoor unit operates as modem connecting the satellite network to the user equipment, i.e., PCs, LANs, phone, fax, etc. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 30 Point-to-point Point-to-point SCPC (single channel per carrier) links are the satellite equivalent of a terrestrial leased line connection. They are usually set-up on a permanent, 24 hour basis and are thus more costly in satellite capacity and less efficient if not used all the time. However, they do support high bandwidths (typically multiples of 2 Mbps) and can easily be used to carry data, voice and even video traffic. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 31 High Altitude Platform Stations HAP located at 21 to 25 km. Communication is between HAP and UT on the ground in a cellular arrangement. Communication also between HAP and a number of gateway stations on the ground, which provide interconnection with the fixed net. Coverage Area UAC SAC RAC 1 – 4 June 2004, Kyiv Elevation Ground range angle (deg) (km) 90 – 30 0 – 40 30 – 15 40 – 90 15 – 5 90 – 220 New Communications Technologies & Implications on Spectrum Monitoring © ADP 32 Operational characteristics Powered by efficient solar cells and regenerative hydrogen-oxygen fuel cells. Electrolysis converts water into fuel during the day and uses it to generate the electrical power needed for night operation. HAPN has a star configuration, with the HAPS platform serving as the main hub. The payload projects multiple spot beams onto the ground and provides ubiquitous coverage over a 150 km diameter. UT are portable devices that communicate with the payload directly. A UT consists of an antenna and a digital interface unit. User-to-user communications are switched directly by the payload, which contains a large ATM switch. Platform payload will have gimballed slotted array antennas with polarizer to ensure proper cross-polarization isolation. The array antennas will project a total of 700 beams in each of the UAC and SAC zones, and selective coverage in the RAC zone. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 33 HAP Network Configuration User devices HAPS platform with communications payload Gateway stations Gateway station WWW PSDN Nearby subscriber set PSTN PSDN: packet switched data network 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 34 HAPN Services The HAPS system is designed to provide variable rate, full duplex, digital channels to homes and the so-called small office/home office (SOHO). The intended services are multimedia applications such as videoconferencing and videophones in addition to high-speed Internet access. The high bit rates, a large metropolitan coverage, and the fact that the user terminals are not dependent upon a ground infrastructure, also makes the HAPS an ideal platform for telecommuting and working-at-home, your own home or your client's home. Therefore, the system is designed to support a large number of virtual local area networks (LANs), so users can access their corporate networks as if they were in the office. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 35 Communication System To maximize spectral efficiency, a dynamic assignment multiple access (DAMA) scheme is used to allow users to share bandwidth efficiently, and there are on-board asynchronous transfer mode (ATM) switches and ATM multiplexers to statistically multiplex the user traffic. UL and DL use QPSK and rate 0.6 concatenated FEC coding (Reed-Solomon + rate 2/3 convolutional coding with constraint length 9). Interleave coding is also used to mitigate burst errors. Because of efficient sharing of bandwidth and the low-duty factor of most types of broadband traffic, all 110,560 users can expect to achieve a maximum upload speed of 2.048 Mbit/s and download speed of 11.24 Mbit/s with a frequency allocation of only 2x100 MHz. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 36 Communication System (cont) Assuming an average of 10% of the total subscriber population to be active at any given time, a single HAPS network can thus support a subscriber population of about one million users given a 2x100 MHz allocation. If the frequency allocation is increased to 2x300 MHz, then a single HAPN can be expected to support more than five million subscribers. The baseline system also includes multiple gateway ground stations which use high-speed synchronous TDM per link for feeder traffic interconnecting HAPN to PSTN and the Internet. The feeder link speed is up to 0.72 Gbit/s for a 300/300 MHz frequency allocation. 64-QAM modulation and rate 0.71 FEC coding are used to optimize the available bandwidth. Additional high-speed point-to-point links can also be provided for corporate customers and service providers. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 37 Communication System (cont) Each uplink TDMA time slot carries one ATM cell. The asynchronous nature of ATM provides great flexibility. For example, no burst time plan is required. The aforementioned DAMA scheme can be integrated with ATM call and traffic management to maximize the efficiency of communication resource management. On the user side, intelligent ATM multiplexers are used to reduce the number of ports on the main switch. Each ATM Mux multiplexes 16 beams into an OC3 (optical carrier, level 3 (155.52 Mbit/s)) port on the switch. At least 44 ports are needed to handle >1 400 beams. The dynamic TDMA turns each beam into a shared bus. Up to 1,000 user terminals can be registered at any time. The design basically requires the ATM Mux to handle the non-standard part of the signalling protocols, so we can use standard ATM switches. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 38 End-to-end networking FIGURE 2 End-to-end networking (2 x 100 MHz allocation, single zone) 2/10 Mbit/s 8 34 Mbit/s 155 Mbit/s Multiplexer - single terminal - small LAN - server and eLAN 16 Multiplexer (1 000) 1 44 Onboard ATM switch 1 Gateway switch 1 Carrier/ISP backbone 15 Gateway switch Router Another subscriber set 11 Gbit/s full duplex, redundant 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 1500-02 39 Ground segment and control The ground system consists of gateway stations and the HAPS control centre. Each gateway station will use high-gain steerable antennas with narrow beams. The RF equipment is similar to those on the payload. The ATM switch required is not large - about four OC3 ports plus whatever is necessary for local servers and/or network management. The HAPS control centre consists of one gateway station to provide communication with the payload and the rest of the system, and four operations and management entities: – The hardware configuration control centre (tracking, telemetry and command of both the platform and the payload). – The communications resource control centre (real-time control of the network resources, e.g. call control, radio resource management, etc.) – The remote ground station control centre (essentially the NOC.) – The regional business centre (financial control, billing, trend analysis.) 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 40 HAPS Network HAPS airship HAPS airship HAPS airship 20 km 367 spot beams 20 deg. HAPS ground station 110 km Footprint or cell in which the same frequency band is used 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 41 DAB production architecture In DAB each service signal is coded individually at source level, error protected and time interleaved in the channel coder. Then the services are multiplexed in the Main Service Channel (MSC), according to a pre-determined, but adjustable, multiplex configuration. The multiplexer output is combined with Multiplex Control and Service information, which travel in the Fast Information Channel (FIC), to form the transmission frames in the Transmission Multimplexer. Finally, Orthogonal Frequency Division Multiplexing (OFDM) is applied to shape the DAB signal, which consists of a large number of carriers each QPSK modulated. The signal is then transposed to the appropriate radio frequency band, amplified and transmitted. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 42 DAB receiver architecture The Figure demonstrates a conceptual DAB receiver. The DAB ensemble is selected in the analogue tuner with the digitized output of which is fed to the OFDM demodulator and channel decoder to eliminate transmission errors. The information contained in the FIC is passed to the user interface for service selection and is used to set up the receiver appropriately. The MSC data is further processed in an audio decoder to produce the left and right audio signals or in a data decoder (Packet Demux) as appropriate. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 43 DAB transmission signal In order to allow the DAB system to be used in different transmission network configurations and over a wide range of operating frequencies, four transmission modes are defined: – – – Transmission mode I with 192 carriers and 96 ms frame duration Transmission modes II with 384 and III with 768 carriers, respectively, both of 24 ms frame duration Transmission mode IV with 1536 carriers and 48 ms frame duration. The DAB signal consists of consecutive Orthogonal Frequency Division Multiplex (OFDM) symbols. The OFDM symbols are generated from the output of the multiplexer which combines the Common Interleaved Frames (CIFs) and the convolutionally encoded Fast Information Blocks (FIBs). Their generation involves the processes of Differential Quadrature Phase Shift Keying (D-QPSK), frequency interleaving, and D-QPSK symbols frequency multiplexing (OFDM generator). The transmission frame consists of a sequence of three groups of OFDM symbols: synchronization channel symbols, Fast Information Channel symbols and Main Service Channel symbols. The synchronization channel symbols comprise the null symbol and the phase reference symbol. The null symbols are also used to allow a limited number of OFDM carriers to convey the Transmitter Identification Information (TII). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 44 DAB radio frequencies Transmission mode I is intended to be used for terrestrial Single Frequency Networks (SFN) and local-area broadcasting in Bands I, II and III. Transmission modes II and IV are intended to be used for terrestrial local broadcasting in Bands I, II, III, IV, V and in the 1,452 – 1,492 MHz frequency band (i.e. L-Band). It can also be used for satellite-only and hybrid satellite-terrestrial broadcasting in L-Band. Transmission mode III is intended to be used for terrestrial, satellite and hybrid satellite-terrestrial broadcasting below 3,000 MHz. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 45 Digital Video Broadcasting DVB uses: – Video compression - MPEG-2 and Audio compression - MPEG Layer II. That means much more TV programmes can be fit into the same channel capacity as analogue TV – A satellite transponder using DVB can contain 6-8 times more TV programmes than analogue TV DVB is also completely digital, opening up the world of Electronic Programme Guides, Internet, data broadcasting, advanced interactive TV, etc. DVB transmission systems: – use the concept of data containers or data pipelines which can carry all kinds of data "quasi-error free" over all kinds of media (satellite, cable, (S)MATV, terrestrial channels, MMDS). – are transparent for SDTV, EDTV, HDTV, for audio at all quality levels and for all kinds of general data. – are part of a family of systems that make use of maximum commonality in order to enable the design of "synergetic" hardware and software. Various standards have been developed, i.e., DVB-T, DVB-C, DVB-S. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 46 DVB Transmission The core of DVB's systems is its series of transmission specifications. First approved in 1994, the DVB-S satellite transmission standard, based on QPSK, is now the de-facto world satellite transmission standard for digital TV applications. The DVB-C, cable delivery mechanism, is closely related to DVB-S, and is based around 64-QAM, although higher order modulation schemes are also supported. DVB-T is the youngest of the three core DVB systems and the most sophisticated. Based on COFDM (Coded Orthogonal Frequency Divisional Multiplexing) and QPSK, 16 QAM and 64 QAM modulation, it is the most sophisticated and flexible digital terrestrial transmission system available today. DVB-T allows services providers to match, and even improve on, analogue coverage, at a fraction of the power. It extends the scope of digital terrestrial television in the mobile field, which was simply not possible before, or with other digital systems. In DVB-T data to be transmitted are first coded with a Reed-Solomon code, interleaved with an additional “outer” interleaver, then passed to the “inner” convolutional coder. At the receiver, the Viterbi decoder is followed by an “outer” interleaver and the “outer” hard decision R-S decoder. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 47 DVB-T signal DVB-T has two modes with either 1705 or 6817 carriers in a 7.61 MHz bandwidth, with a wide range of guard intervals from 7 to 224 µs. Coherent demodulation is used, with QPSK / 16-QAM / 64-QAM constellations. In conjunction with options for inner-code rate, this provides extensive trade-off between ruggedness and capacity (from 5 to 31.7 Mbit/s). The figures quoted above relate to the use of nominally 8 MHz channels. The DVB-T specification can be adapted to 6 or 7 MHz channels by simply scaling the clock rate; the capacity and bandwidth then follow in the same proportion. 1 – 4 June 2004, Kyiv 0dB *ATTEN RL -20.0dBm 10dB/ MKR 1 646.19 MHz MKR 2 653.81 MHz MKR DELTA 7.63 MHz .16 dB CENTER 650.00MHz *RBW 3.0kHz SPAN VBW 3.0kHz New Communications Technologies & Implications on Spectrum Monitoring © ADP 10.00MHz SWP 48 2.8sec Digital Convergence With the arrival of the era of Digital Convergence, emerging new technologies are blurring the boundaries between the traditionally separate communication platforms of the computing, broadcasting, and telecommunications industries. Mobile communication in particular is increasingly becoming the driver for this process. DVB 2.0 is DVB’s consortium take on Digital Convergence, and consists of a roadmap for the development of digital broadcasting technology in the converging world of today. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 49 DVB-X, the mobile DTV DVB is addressing the technology developments with respect to mobile communication. GPRS and UMTS will be able to offer various multimedia services. Ad Hoc groups are assessing how GPRS and UMTS can work with DVB systems, and are looking at the service convergence and network cooperation between these platforms. In addition to the 3G networks, Wireless Local Area Networks are gaining in importance and are taken into account in DVB activities. DVB over IP and IP over DVB specifications are being developed. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 50 UMTS services UMTS offers teleservices (like speech or SMS) and bearer services, which provide the capability for information transfer between access points. It is possible to negotiate and renegotiate the characteristics of a bearer service at session or connection establishment and during ongoing session or connection. Both connection oriented and connectionless services are offered for Point-to-Point and Point-to-Multipoint communication. Bearer services have different QoS parameters for maximum transfer delay, delay variation and bit error rate. Offered data rate targets are: – 144 kbits/s satellite and rural outdoor – 384 kbits/s urban outdoor – 2048 kbits/s indoor and low range outdoor 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 51 UMTS network services UMTS network services have different QoS classes for four types of traffic: – – – – Conversational class (voice, video telephony, video gaming) Streaming class (multimedia, video on demand, webcast) Interactive class (web browsing, network gaming, database access) Background class (email, SMS, downloading) UMTS will also have a Virtual Home Environment (VHE). It is a concept for personal service environment portability across network boundaries and between terminals. Personal service environment means that users are consistently presented with the same personalized features, User Interface customization and services in whatever network or terminal, wherever the user may be located. UMTS also has improved network security and location based services. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 52 UMTS architecture A UMTS network consist of three interacting domains; Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE). The main function of the core network is to provide switching, routing and transit for user traffic. Core network also contains the databases and network management functions. The basic Core Network architecture for UMTS is based on GSM network with GPRS. The UTRAN provides the air interface access method for User Equipment. Base Station is referred as Node-B and control equipment for Node-B's is called Radio Network Controller (RNC). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 53 TETRA TErrestrial Trunked RAdio (TETRA) is the modern digital Private Mobile Radio (PMR) and Public Access Mobile Radio (PAMR) technology for police, ambulance and fire services, security services, utilities, military, public access, fleet management, transport services, closed user groups, factory site services, mining, etc. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 54 TETRA specification TETRA offers fast call set-up time, addressing the critical needs of many user segments, excellent group communication support, Direct mode operation between radios, packet data and circuit data transfer services, frequency economy and excellent security features. TETRA uses Time Division Multiple Access (TDMA) technology with 4 user channels on one radio carrier and 25 kHz spacing between carriers. This makes it inherently efficient in the way that it uses the frequency spectrum. The modulation scheme is π/4-shifted Differential Quaternary Phase Shift Keying (π/4-DQPSK) with root-raised cosine modulation filter and a roll-off factor of 0,35. The modulation rate is 36 kbit/s. TETRA trunking facility provides a pooling of all radio channels which are then allocated on demand to individual users, in both voice and data modes. By the provision of national and multi-national networks, national and international roaming can be supported, the user being in constant seamless communications with his colleagues. TETRA supports point-to-point, and point-to-multipoint communications both by the use of the TETRA infrastructure and by the use of Direct Mode without infrastructure. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 55 TETRA architecture 1b 3 1a BS BS NMS BS BS BS BS 5 2 6 PSTN, ISDN PDN 1 – 4 June 2004, Kyiv 4 .Another TETRA Network Remote Line Station (Despatcher) New Communications Technologies & Implications on Spectrum Monitoring © ADP 56 TETRA V+D air interface Air Interface V Uplink D TETRA Infrastructure TDMA FRAME V TS 1 D TS 2 D TS 3 V TS 4 V V D 1 – 4 June 2004, Kyiv Downlink TS = Time Slot New Communications Technologies & Implications on Spectrum Monitoring © ADP 57 Air interface variants DMO AIR I/F TMO AIR I/F PEI 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 58 TETRA in 3G era Network Management Service Nodes Customer Care Billing UMTS Core Network Transit Layer GSM Access Network Management Gateway TETRA Infrastructure UMTS Access TAPS Access 1 – 4 June 2004, Kyiv TETRA1 Access New Communications Technologies & Implications on Spectrum Monitoring © ADP TETRA1 +TEDS Access 59 TETRA Spectrum For emergency systems in Europe the frequency bands 380-383 MHz and 390-393 MHz have been allocated for use by a single harmonized digital land mobile systems by the ERC Decision (96)01. Additionally, whole or appropriate parts of the bands 383-395 MHz and 393-395 MHz can be utilized should the bandwidth be required. For civil systems in Europe the frequency bands 410-430 MHz, 870-876 MHz / 915-921 MHz, 450-470 MHz, 385390 MHz / 395-399,9 MHz, have been allocated for TETRA by the ERC Decision (96)04. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 60 Bluetooth Bluetooth is a short-range radio link intended to replace the cables connecting portable and/or fixed electronic devices. Key features are robustness, low complexity, low power and low cost. Bluetooth operates in the unlicensed ISM band at 2.4 GHz. Although globally available, the exact location and the width of the band may differ by country. In the US and Europe (including UK), a band of 83.5 MHz is available; in this band 79 RF channels spaced 1 MHz apart are defined. A frequency hop transceiver is applied to combat interference and fading. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 61 Modulation characteristics A Gaussian shaped, binary FSK modulation is applied with a BTs product of 0.5 to minimize transceiver complexity. A binary one is represented by a positive frequency deviation, a binary zero by a negative frequency deviation. The maximum frequency deviation should be between 140 kHz and 175 kHz and never less than 115 kHz. The symbol rate is 1 Ms/s. A slotted channel is applied with a nominal slot length of 625 μs. For full duplex transmission, a Time-Division Duplex (TDD) scheme is used. On the channel, information is exchanged through packets. Each packet is transmitted on a different hop frequency. A packet nominally covers a single slot, but can be extended to cover up to five slots. The Bluetooth protocol uses a combination of circuit and packet switching. Slots can be reserved for synchronous packets. Bluetooth can support asynchronous data channel, up to three simultaneous synchronous voice channels, or a channel which simultaneously supports asynchronous data and synchronous voice. Each voice channel supports 64 kb/s synchronous (voice) channel in each direction. The asynchronous channel can support maximal 723.2 kb/s asymmetric (and still up to 57.6 kb/s in the return direction), or 433.9 kb/s symmetric. The Bluetooth system consists of a radio unit, a link control unit, and a support unit for link management and host terminal interface functions. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 62 Bluetooth transmitter Each device is classified into 3 power classes, Power Class 1, 2 & 3. – Power Class 1: is designed for long range (~100m) devices, with a max output power of 20 dBm, – Power Class 2: for ordinary range devices (~10m) devices, with a max output power of 4 dBm, – Power Class 3: for short range devices (~10cm) devices, with a max output power of 0 dBm. The Bluetooth radio interface is based on a nominal antenna power of 0dBm. Each device can optionally vary its transmitted power. Equipment with power control capability optimizes the output power in a link with LMP commands. It is done by measuring RSSI and report back if the power should be increased or decreased. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 63 Bluetooth receiver Sensitivity Level: The receiver must have a sensitivity level for which the bit error rate (BER) 0.1% is met. For Bluetooth this means an actual sensitivity level of -70dBm or better. Interference Performance: The interference performance on Co-channel and adjacent 1 MHz and 2 MHz are measured with the wanted signal 10 dB over the reference sensitivity level. On all other frequencies the wanted signal shall be 3 dB over the reference sensitivity level. Out-of-Band blocking: The out-of-band blocking is measured with the wanted signal 3 dB over the reference sensitivity level. The interfering signal shall be a continuous wave signal. The BER shall be less than or equal to 0.1%. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 64 BRAN – HIPERLAN/1 HIPERLAN Type 1 is a Radio LAN standard designed to provide high-speed communications (20 Mbit/s) between portable devices in the 5 GHz range. It is intended to allow flexible wireless data networks to be created, without the need for an existing wired infrastructure. In addition it can be used as an extension of a wired LAN. The support of multimedia applications is possible. HIPERLAN/1 devices may be operated in Europe in the 5.15 – 5.30 GHz frequency band according to CEPT Recommendation T/R 22-06. Five HIPERLAN/1 channels may be accommodated in the 5.15 – 5.30 GHz band. Channels 0, 1, 2 are the mandatory default channels. The availability of channels 3, 4 is subject to national administrations. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 65 HIPERLAN/1 Physical Layer: Data is transmitted in bursts containing a number of FSK-modulated low rate bits and a GMSK (BT=0,3) high rate bit stream comprising a synchronization/training sequence of 450 bits and data blocks of 496 interleaved, BCH(31,26)-coded bits. Each burst is built from a CAC PDU. The signalling rate for high rate transmission is 23.5 Mbps (this results in net data rates approximately up to 20 Mbit/s) and the low signalling rate 1.47Mbps. Nominal carrier bandwidth is 23.5 MHz. Specification: The HIPERLAN/1 Functional Specification is contained in EN 300 652. Type approval requirements and protocol conformance testing specifications are covered in the ETS 300 836 series. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 66 BRAN – HIPERLAN/2 HIPERLAN/2 is a flexible Radio LAN standard designed to provide high speed access (up to 54 Mbit/s at PHY layer) to a variety of networks including 3G mobile core networks, ATM networks and IP based networks, and also for private use as a wireless LAN system. Basic applications include data, voice and video, with specific QoS parameters taken into account. HIPERLAN/2 systems can be deployed in offices, classrooms, homes, factories, hot spot areas like exhibition halls and more generally where radio transmission is an efficient alternative or a complement to wired technology. HIPERLAN/2 marks a significant milestone in the development of a combined technology for broadband cellular short-range communications and wireless Local Area Networks (LANs) which will provide performance comparable with that of wired LANs. Since the 5 GHz band to be exploited by the HIPERLAN/2 standard is allocated to wireless LANs world-wide, HIPERLAN/2 has the potential to enable the success of wireless LANs on a global basis. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 67 HIPERLAN/2 Modes of operation: HIPERLAN/2 relies on cellular networking topology combined with an ad-hoc networking capability. It supports two basic modes of operation: centralized mode and direct mode. The centralized mode is used in the cellular networking topology where each radio cell is controlled by an access point covering a certain geographical area. In this mode, a mobile terminal communicates with other mobile terminals or with the core network via an access point. This mode of operation is mainly used in business applications, both indoors and outdoors, where an area much larger than a radio cell has to be covered. The direct mode is used in the ad-hoc networking topology, mainly in typical private home environments, where a radio cell covers the whole serving area. In this mode, mobile terminals in a single-cell home "network" can directly exchange data. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 68 HIPERLAN/2 Physical layer: The signal modulation is based on the Orthogonal Frequency Division Multiplexing (OFDM) with several sub-carrier modulation and forward error correction combinations that allow to cope with various channel configurations. The main parameters have the following values: – FFT size: 64. – Number of used sub-carriers: 52, where 48 sub-carriers are used for data and the rest for pilots. – Channel Spacing: 20 MHz. – Sampling rate: 20 Msamples/s. – Guard interval: 800 ns default mode corresponding to 16 time samples; 400 ns as an option. – Sub-carrier modulation: BPSK, QPSK, 16QAM and optionally 64QAM. – Sub-carrier demodulation: Coherent. – Mandatory Forward Error Correction: a rate 1/2, constraint length 7 mother convolutional code (9/16 and 3/4 by code puncturing). – Supported data rates: 6, 9, 12, 18, 27, 36, 54 Mbit/s. – Interleaving: Block interleaving with the size of one OFDM symbol. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 69 HIPERLAN/2 Radio & Spectrum HIPERLAN/2 can support multi beam antennas (sectors) to improve the link budget and to reduce interference in the radio network. It also defines a set of protocols (measurements and signalling) to provide support for a number of radio network functions, e.g. Dynamic Frequency Selection (DFS), link adaptation, handover, multi beam antennas and power control, where the algorithms are vendor specific. To cope with the varying radio link quality (interference and propagation conditions), a link adaptation scheme is used. Based on link quality measurements, the physical layer data rate is adapted to the current link quality. Transmitter power control is supported in both mobile terminal (uplink) and access point (downlink). The 5 GHz band is open in Europe, the United States and Japan. The current spectrum allocation at 5 GHz comprises 455 MHz in Europe, 300 MHz in the US, and 100 MHz in Japan. The PHY layer of IEEE 802.11 standard in the 5 GHz band is harmonized with that of HIPERLAN/2. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 70 BRAN – HIPERACCESS HIPERACCESS is a standard for broadband multimedia fixed wireless access. The HIPERACCESS specifications will allow for a flexible and competitive alternative to wired access networks. When finalized, HIPERACCESS will be an interoperable standard, in order to promote a mass market and thereby low cost products. HIPERACCESS is targeting high frequency bands, especially it will be optimized for the 40,5 - 43,5 GHz band. ETSI’s BRAN is co-operating closely with IEEE-SA (Working Group 802.16) to harmonize the interoperability standards for broadband multimedia fixed wireless access networks. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 71 BRAN – HIPERMAN HIPERMAN will be an interoperable broadband fixed wireless access system operating at radio frequencies between 2 GHz and 11 GHz. The HIPERMAN standard is designed for Fixed Wireless Access provisioning to SMEs and residences using the basic MAC (DLC and CLs) of the IEEE 802.16-2001 standard. It has been developed in very close cooperation with IEEE 802.16, such that the HIPERMAN standard and a subset of the IEEE 802.16a-2003 standard will interoperate seamlessly. HIPERMAN is capable of supporting ATM, though the main focus is on IP traffic. It offers various service categories, full Quality of Service, fast connection control management, strong security, fast adaptation of coding, modulation and transmit power to propagation conditions and is capable of non-line-of-sight operation. HIPERMAN enables both PMP and Mesh network configurations. HIPERMAN also supports both FDD and TDD frequency allocations and HFDD terminals. All this is achieved with a minimum number of options to simplify implementation and interoperability. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 72 BRAN – Standards summary HIPERACCESS – This long range variant is intended for point-to-multipoint, high speed access (25 Mbit/s typical data rate) by residential and small business users to a wide variety of networks including the UMTS™ core networks, ATM networks and IP based networks (HIPERLAN/2 might be used for distribution within premises). Spectrum allocation in the 40,5 - 43,5 GHz band are being discussed in the relevant CEPT working groups. HIPERMAN – This will be an interoperable broadband fixed wireless access system operating at radio frequencies between 2 GHz and 11 GHz. The air interface will be optimized for PMP configurations, but may allow for flexible mesh deployments. The HIPERMAN standards specify the PHY and DLC layers, which are core network independent, and the core network specific Convergence sublayers. HIPERLINK – This variant will provide short-range very high-speed interconnection of HIPERLANs and HIPERACCESS, e.g. up to 155 Mbit/s over distances up to 150 m. Spectrum for HIPERLINK is available in the 17 GHz range. The work on HIPERLINK standardization has not started yet. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 73 Regulatory implications With the introduction of numerous new radio applications, including short range devices and technologies, interference and emission issues become significant. In order to ensure the harmonious co-existence of established and new services and technologies, international organizations such as the IEC and ITU, and regulatory bodies such as the RA of the UK commissioned theoretical studies and practical measurement campaigns. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 74 CISPR – Aims To promote international agreement on the aspects of radio interference set out hereafter, thereby facilitating international trade. – 1) Protection of radio reception from interference sources such as: • • • • electrical appliances of all types; ignition systems; electricity supply systems, including electric transport systems; industrial, scientific and electromedical radiofrequency (excluding radiation from transmitters intended for conveying information); • sound and television broadcasting receivers; • information technology equipment. – 2) Equipment and methods for the measurement of interference. – 3) Limits for interference caused by the sources listed in item 1). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 75 CISPR – Aims (cont) To promote international agreement on the aspects of radio interference set out hereafter, thereby facilitating international trade. – 4) Requirements for the immunity of sound and television broadcast receiving installations from interference and the prescriptions of methods of measurement of such immunity. – 5) Where possible overlap arises in the standards adopted by the CISPR and other IEC and ISO Technical Committees, the consideration jointly with those Committees of the emission and immunity requirements for devices other than receivers. – 6) Impact of safety regulations on interference suppression of electrical equipment. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 76 Interference from new wireline communications applications Interference may be generated by new communications applications offered over existing wired infrastructure, such as xDSL, PLT/PLC. For the harmonious co-existence of existing, new and future microwave communications applications, emission limits in the frequency range 1 GHz - 18 GHz need to be established. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 77 Interference from UTTNs D Welsh, I D Flintoft and A D Papatsoris, ‘Cumulative Effect Of Radiated Emissions From Metallic Data Distribution Systems On Radio Based Services’, Final report for Radio Communications Agency contract AY3525, Document No R/00/026, Project No 1191, University of York, May 2000, (http://www.ofcom.org.uk/static/archive/ra/topics/research/topics/emc/ay3525/intro.h tm). I D Flintoft, D Welsh, and A D Papatsoris, ‘Accumulated Emissions From Metallic Data Delivery Systems To Verify The Angle Of Radiation Of ADSL Systems And Their Potential Effect On Aeronautical Services’, final report for Radiocommunications Agency contract AY3525, University of York, July 2000, (http://www.ofcom.org.uk/static/archive/ra/topics/research/topics/emc/ay3525/report 2.doc). M H Capstick, I D Flintoft, and A D Papatsoris, ‘Specification of the Scope of Work Needed to Determine the Technical and Operational Impact of Emissions from Unstructured Telecommunication Transmission Networks Interfering with Aeronautical and Maritime Radio Services in the UK’, final report for Radiocommunications Agency contract AY4075, 3rd Issue, University of York, May 2002, (http://www.ofcom.org.uk/static/archive/ra/topics/research/topics/emc/ay4075final.p df). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 78 UTTN emissions 5.5 20 10 5 15 15 25 20 3.5 20 20 15 10 15 25 25 2.5 20 2 20 1.5 20 15 25 20 25 25 10 0 0.5 1 10 0 1.5 2 15 10 5 London 0 15 0.5 20 Berlin 15 20 1 25 electric field strength, [dBuV/m] 10 25 20 3 2.4 MHz 4.8 MHz 8.4 MHz 20 15 vertical distance, [km] 4 10 15 4.5 25 25 5 30 20 2.5 3 3.5 horizontal distance, [km] 20 4 -5 4.5 5 5.5 0 100 200 300 400 500 600 distance, [km] 700 800 900 1000 Left. Cumulative downstream ADSL electric field contour plot at 1 km above ground. Right. Cumulative sky wave PLT emission electric field reaching London from Berlin. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 79 Emission limits for 1 – 18 GHz CISPR aims: 3) Limits for interference caused by the sources listed in item 1). A J Rowell, D W Welsh, and A D Papatsoris, ‘Practical Limits for EMC Emission Testing at Frequencies Above 1 GHz’, final report for Radiocommunications Agency contract AY1255, University of York, November 2000, (http://www.ofcom.org.uk/stat ic/archive/ra/topics/research/t opics/emc/ay3601/ay3601.pdf ). 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 80 SMon & Signal Analysis Signal analysis is the process of extracting every possible bit of transmitted information from a radio signal. The information to be extracted can be the intentionally transmitted information or information of technical nature. Communication is organised in different layers of the OSI model. Therefore signal analysis can also be organised in different layers like detection, spectrum analysis, modulation recognition, analogue and digital demodulation, code recognition and channel decoding. Correlation analysis and cryptography are to some extent part of the subject. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 81 Signal analysis system (SAS) Since the monitoring services of the different administrations have different needs, a signal analysis system should be open and flexible in both physical construction and functionality. A DSP based system with upgradeable and re-configurable hardware and software is the best choice. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 82 SAS specification A SAS consists of a wide band and a narrow band analyser, which can be implemented as separate systems or integrated in one system. Wide band receiving increases the detection probability of short time signals or burst signals (such as GSM traffic) in a wide frequency range. It makes the analysis of communications relations (e.g. duplex on different frequencies) possible. Wide band receiving is needed for example for wide band CDMA signals, frequency hopping communications or chirp signals. Narrow band receiving has a better performance in dense scenarios (for example the HF frequency range). Although narrowband performance can be obtained by applying filtering techniques on the signals sampled from the wide band analyser you have to make sure that in this case the wideband analyser is not overloaded by strong signals. Dependent of the needs of the monitoring service only one or both analysers can be implemented. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 83 SMon of satellite emissions The broadband analyzer performs: – – – LNA / LNB LNA / LNB RF matrix 1 - 18 GHz (40 GHz) Positionneur Positioner 1 - 3 GHz SHF Receiver IF 70 or 140 MHz Splitter Set of standard demodulators and decoders V/UHF receiver Wide band analyser 40 MHz Narrow-band analyser signal analysis: – – – – – – – – band segmentation; level measurement; bandwidth measurement; modulation rate measurement; modulation characterization; channel/noise ratio measurement; channel/interference ratio measurement; and interference analysis (modulation rhythm and carrier frequency measurements). Console DVB demodulators Sensors Control stations Ethernet 100 mbits/s broadband signals acquisition up to 40 MHz on the 70 MHz IF at the output of the receiver and its digitization; display of the broadband spectrum in the instantaneous bandwidth of the SHF receiver (40, 20, 15, 10, or 5 MHz); polarization determination through the control of the feeders; LNA / LNB LNA / LNB Switch matrix Off-line analysis station Firewall RS232 concentrator Sensor remote control Sat software station 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 84 SMon of Fixed Links Analogue links are typically frequency modulated with a base-band signal of several or many multiplexed traffic channels. For multi-channel audio communications, the base-band structure follows established group, master-group, and super-group conventions as defined by the ITU Telecommunications Standardization Sector (ITU-T). Digital links display only a band of spectral occupancy visually similar to filtered white noise. It is not immediately evident from RF spectra whether any of the separate base-band channels are occupied or not. It is necessary to discuss the construction of these signals before any analysis is considered. The source will typically be a single multiplexed digital signal as described by ITU-T Recommendation G703. Similarly, digital modulation methods are equally varied, but may be consistent in any one band, depending on national spectrum management policy. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 85 SMon of fixed links Monitoring of these transmissions has to be from mobile units, because of the reduced and narrowed geographical area covered by the transmitted signal at levels that can be received. Normally, to measure such a system, the monitoring antenna has to be in the beam from the microwave transmitting antenna, or otherwise closely coupled to the transmitter or feed line. In general, basic parameters to be measured are : – – – – – – – Analyzing equipment Filter Spectrum Analyzer LNA Calibration input carrier frequency, field strength or power flux density, occupied bandwidth, deviation from assigned frequency, observed polarisation, class of emission identification of signal source. Two common methods are used: – – Antenna system Antenna system Analyzing equipment RF mixer Spectrum analyzer Signal Analyzer Receiver LNA IF port Calibration input Direct intercept Intercept with mixer 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 86 SMon of Mobile Communications The minimum capabilities required to monitor a digital cellular telephone or PCS system for regulatory compliance is an antenna and either an RF spectrum analyzer or digital receiver with bandwidth sufficient for the type of system in use, and analysis capability in both the time and frequency domains. A somewhat more sophisticated monitoring station will have the additional capability to measure received signal strength, determine occupied bandwidth, and have directional antennas to minimize interference. In addition, a capability to perform direction-finding on the source of emissions is highly desirable. A sophisticated station equipped to monitor digital cellular and PCS systems must have wideband digital signal acquisition and analysis capability in time, frequency, and phase domains. Of particular value is the capability to decode and display the constellations of the complex digital modulation schemes to aid in positive identification (vector signal analysis). A fully equipped station will have equipment capable of detecting, demodulating, direction-finding (locating), and analyzing wide bandwidth direct sequence and frequencyhopping spread spectrum signals. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 87 Multimedia SMon Multimedia monitoring could be included in an administration’s typical radio and television technical monitoring activities. This could include reception, decoding, processing, recording and eventual analysis of broadcast, fixed and mobile service transmissions carrying multimedia. The same monitoring principles apply directly to broadcasting conducted by wireless cable television, satellite systems, and any other means of wireless Internet distribution. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 88 SMon of Multimedia A multimedia monitoring system would need to be based on the up-todate technologies of multimedia video and radio broadcast processes, including of MPEG coding/decoding , TCP/IP and HTML/Web. A multimedia monitoring system should have the ability to characterize a multimedia network by observing, for example, the following system characteristics: – – – – – – client-server distribution architecture; web servers (Internet and Intranet transaction server); TCP/IP network; multicast (point to multipoint); unicast (point to point); and streaming. By means of appropriate hardware and software, the multimedia monitoring system would need the ability to intercept and record information automatically, and at the appropriate time, restore the information for analysis. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 89 Conclusions New communications technologies and applications require advanced vector signal analysis techniques to be decoded. This dictates the need for sophisticated hardware and highly specialised and expensive software. It also requires the development of new skills to spectrum monitoring personnel and suggests that Administrations should adopt a continuous learning approach for their staff. In a rapidly changing spectrum management field, Administrations might wish to consider a new framework of national strategy, in which the focus has shifted from discovering and eliminating interference to measuring sustainable – tolerable interference. 1 – 4 June 2004, Kyiv New Communications Technologies & Implications on Spectrum Monitoring © ADP 90