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Implementation of Mobile Terminal in a Wireless Mobile Networks SUN-MI JUN NAM-HOON PARK Electronics and Telecommunications Research Institute 161 Gajeong-Dong, Yuseong-Gu, Daejeon Republic of Korea Abstract: - Nowadays, there are many efforts to develop wireless mobile networks in which the existing Internet services can be applicable. However, the existing Windows based PC is not suitable to support the seamless service in the wireless mobile network. To support the seamless Internet, the terminal should change its network configuration and update location whenever handoff procedures. We develop an appropriate mobile terminal based on Windows. In our developing wireless mobile network, there are two types of packets delivered to the terminal. One type is traffic packets loaded on IP protocol. The other is control packet which takes a part of controlling the terminal such as initiating , terminating sessions, and management. The terminal should monitor the radio states and diagnose the terminal states. We propose to modify the NDIS library, which is Windows network adaptation library, to receive and process the control packets for our developing network. We also introduce the additional software blocks to control the terminal such as the radio states monitor, debug monitor, and the Mobile IP client. Key-Words: - Wireless mobile network, mobile terminal, NDIS 1 Introduction The fast growth of the Internet users and the rapid development of the wireless technologies are increasing the needs of the Internet service on the wireless mobile network such as WiBro in Korea [1]. The various kinds of service based on the Internet are tried to adapt on the wireless mobile network. There are many efforts to adapt the IP based service to the wireless mobile network. HA packets Edge Router Internet Server AAA PAR 1 BS0 BS1 PAR 2 packets BS2 MT Move to new BS Move to new PAR Fig. 1 A Service example in Wireless Mobile Network The seamless service for a mobile terminal requires the pre-negotiated QoS between a server and a terminal. But the mobile terminal should implement the handoff procedures during its moving and these cause the handoff latency which is a factor of transmission delay. Fig. 1 presents an example of the architecture of wireless mobile network, WiBro [1]. Terminals are connected to a BS (Base Station) through a wireless interface and an aggregation of BSs is connected to a PAR (Packet Access Router or Mobile switch Center) through a wired interface. PAR manages BSs and terminals and also allows them to access the public Internet. A mobile terminal implements handoff operations from a BS to another BS while moving [1][2][3]. The existing applications and management suites of the notebook or PDA are not suitable to the wireless mobile network. The terminal control programs for mobility should be required and the modification of the existing TCP/IP protocol suite should be also required. This paper presnets a design of the mobile mobile terminal based on Windows PC or PDA and the implementation result. Chapter2 shows some considerations of the mobile terminal suitable to wireless mobile environment, Chapter3 describes our design feature of the mobile terminal, Chapter 4 shows the implementation result. 2 Considerations The based on the general purpose OS has limitation to support the seamless service, because the general purpose platform has insufficiecy in terminal mobility. The terminal also should be compatible with the existing application program and service. If the terminal platform is based on the x86 processor and Windows OS, the off-the-shelf services and applications should be adapted to the wireless mobile network. As a result, we modify the existing platform of the terminal suitable to the wireless mobile environment. This chapter introduces some considerations to develop the mobile terminal platform. - - - Wireless modem and RF interface are located in a NIC(Network Interface Card) which can be connected with the various types of terminals easily. The terminal should imform the user of the radio rx/tx states. The terminal also should have the Terminal Control Process which controls the entire signalling procedure of the wireless internet networking such as Mobile IP, initiating and terminating wireless service. The adaptation layer is required between the NIC driver and the TCP/IP protocol suite. This layer analyzes the packets from the NIC, classifies them into appropriate TCP/IP queues and the Terminal Control Process. The terminal is divided into two parts. One is MTS (Mobile Terminal Subsystem), which has RF device, the modem, and MAC protocol layer, and located in PCMCIA card. The other is TES (Terminal Equipment Subsystem) with the Terminal Control Process, the mobile IP client and the Internet protocol, which is located in the portable PC or PDA. The design of the TES is detailed in Chapter 3. 3 Design of the Mobile Terminal We implement the TES based on the Windows XP notebook PC. TES should have some function blocks presented in Fig. 3. Especially, the following two blocks, the modified NDIS and RSMB should be created and developled newly. The other blocks are implemented using the existing standards or recommendations . 3.1 IP adaptation and NDIS modification User space We design the structure of the mobile terminal as the following Fig. 2. TES Fig. 3 IP Adaptation layer and NDIS layer Use Ap A. The original NDIS Windows-based operating systems support several types of kernel-mode network drivers. The Network Driver Interface Specification (NDIS) library abstracts the network hardware from network drivers. NDIS also specifies a standard interface between layered network drivers, thereby abstracting lower-level drivers that manage hardware from upper-level drivers such as network transports. NDIS also maintains state information and parameters for network drivers, including pointers to functions, handles, and parameter blocks for linkage, and other system values. Kernel Equipm TES (Terminal space Windows Application Programs Fig. 2 The structure of the mobile terminal T Mobile A NDIS miniport driver (also called a miniport driver) has two basic functions: Managing a network interface card (NIC), including sending and receiving data through the NIC. Interfacing with higher-level drivers, such as intermediate drivers and transport protocol drivers, a miniport driver communicates with its NIC and with higher-level drivers through the NDIS library[7]. B. The modified NDIS In WiBro, there are two types of packets delivered to the terminal. One type is the traffic packets loaded on IP protocol. The other is the control packet which takes a part of controlling the terminal such as initiating and terminating sessions, and authenticating. They also monitor the radio states and diagnose the terminal states. However, the original NDIS cannot process the control packets of WiBro and deliver them to the Terminal Control Process. We modify the original NDIS layer so that it processes not the IP traffic packets, but also the control packets. This NDIS layer classifies the packets from NIC into the IP packets and the control packets. The IP packets are delivered to the TCP/IP protocol suite, and the control packets are delivered to the predefined file shared with the Terminal Control Process. The following picture is the proposed software architecture of the mobile terminal, which has the modified NDIS layer and the additional file I/O system shared with Terminal Control Process. Terminal Control Process initiates and terminates WiBro service. This process authenticates the device or the user and also monitors the radio states and diagnoses the terminal execution states. Terminal Control Process NIC Initilization Service Authentication/RSM/ DM Initiation Mobile IP Release Mobile IP Initiation Terimnation Fig. 5 The sequence of the Terminal Control Process Fig. 5 is the sequence of the operations of Terminal Control Process. This process is an application program located in TES, initializes the Network Interface Card and the WiBro service. This process executes the Mobile IP transaction which initiates the Internet service through the public network. This process terminates the service by doing the Mobile IP release operation. This process monitors the radio states and the terminal execution or debug messages. These additional blocks are detailed in the next sections. 3.3 Radio States Monitoring Block For the purpose of Radio States Management, there are The details of the modified NDIS layer are introduced the following picture, Fig. 4. User App Fig. 4 The modification of the NDIS layer 3.2 Terminal Control Process some parameters concerning wireless environment to be monitored, and user can change the connection modes manually or automatically. The required radio parameters are shown as below, Signal strength (dBM) Tx rate (Kbit/s) Tx Packet Amount (Kbyte) Tx Packet Error rate (%) Rx rate (Kbit/s) Rx Packet Amount (Kbyte) Rx Packet Error rate (%) User App This block polls and receives the radio states from the wireless modem periodically to update its monitoring tasks. The updated results are displayed in a near real-time delay with a maximum delay in the TES (host computer) equal to the polling interval to reflect the current radio environment states. Socket Interfa When it finished to prepare the service start, by RSMRequest signal from the host main process, the state transition takes place for all processes to ready to working state from Null state. Then, by sending CIBDataReq primitive, RSM entity is able to receive data frame from the Modem (NIC). CIBDataReq primitive is used to request that an upper layer PDU be sent using the procedures for the information transfer service. CIBDataInd primitive indicates the arrival of Radio state parameters received within one transmission time interval by means of the information transfer periodically. Terminal Control Process RSMB NIC NDIS Fig. 8 The dialog for user information (Authentication, AAA Key, Mobile IP) (Service Start) StartRSMRequest Selectively CIBDataReq RSMB Message CIBDataReq RSMB Message CIBDataInd RSMB Message StartRSMResponse CIBDataInd RSMB Message CIBDataInd RSMB Message Periodically CIBDataInd RSMB Message Fig. 9 The Radio States Monitor Dialog 5 Conclusion Fig. 6 Message sequences chart of RSMB 4 Implementation The mobile termianl is implemented using Visual Studio, Windows DDK and SDK based on Windows XP. The following features are the presentation of the mobile termianl. Fig. 7 The Terminal Control Process This paper shows a design and implementation of the mobile terminal suitable to wireless mobile network. This terminal is implemented using the existing platform such as x86 notebook PC and Windows XP OS. There is no network development package or protocol suite for wireless mobile environment. As a result, we show the development of some additional controlling process for networking signaling and the radio states monitor, and we mention the need of the modification of the existing NDIS library of Windows XP. We are now developing WiBro, wireless mobile network, using the mobile terminal introduced in this paper. References: [1] ETRI, TTA, Specifications for 2.3GHz band Highspeed Portable Internet Service, 2004. 4. [2] IEEE, Part16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE Standards, 2001 [3] IEEE 802.16 TGe Working Document : Part 16 : Air Interface for Broadband Wireless Access Systems, Amendment 4-Mobility Enhancements [4] J.S. Kim, “Design of Radio Status Management System for Highspeed Wireless Mobile Terminal”, WWC,Vol1, 2004 [5] C. Eklund, R. B. Marks et al.: “IEEE Standard 802.16:A Tech-nical Overview of the TM WirelessMAN Air Interface for Broad-band Wireless Access”, IEEE Comm. Mag., June, 2002, pp.98-107. [6] A. Rubini, J. Corbet, Linux Device Drivers - The 2nd Edition, O’Reilly. [7] Network Devices and Protocols: Windows DDK, MS Press