An Implementation of the Subscriber Station MAC Protocol in the Wireless MAN
Yousun Hwang, Eung-bae Kim · 한국통신학회 학술대회논문집 · 2003
The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. IEEE Standard 802.16, with its WirelessMANTM air interface, set the stage for widespread and effective deployments worldwide. This paper presents an implementation of media access control that can be applied to WirelessMAN. Medium access control is a key issue in multi-access networks where a common channel is shared by many users. The designed MAC prototype roughly consists of MAC H/W and MAC S/W. The MAC H/W part includes timing process, MAC transmission control, MAC reception control, and CRC/HCS process. The MAC S/W part includes control of MAC signaling, network interface, and PHY control. The designed MAC protocol will be integrated with the PHY of BWA in future and we can test overall system performance of MAC and PHY. 1. INTRODICTION The recent shakeout in the fixed wireless industry has prompted the question of whether the right technology is applied tin the last mile wireless access. The key to the success of BWA is to offer a solution at least as reliable and easy to deploy as the competitive copper technologies. BWA System Based on IEEE 802.16 supports the three method of transmission, the Framed FDD, Unframed FDD and TDD. In the TDD system, the uplink and downlink transmission share the same frequency but are separated in time. A TDD frame has a fixed duration and contains one downlink and one uplink subframe, the TDD framing is adaptive in that the link capacity allocated to the downlink versus the uplink may vary. In order to minimize the complexity of the radio-frequency elements at the subscriber station (SS) the uplink and downlink carrier frequencies shall reference each other and there are also exists an initial ranging processor frequency and power calibration. After the initial frequency has been calibrated, periodic measurements of the frequency offset value at the Base Station (BS) shall be made by the physical layer and sent to the SS via a MAC message. To develop the WirelessMAN system, there need several key technologies such as modulation, RF/IF technology, and medium access control technology. Especially, MAC is a key issue in multi-access networks where a common channel shared by multiple users. MAC protocol is a set of rules that coordinates the transmissions of all users so that the common channel is efficiently utilized [1]. This paper is organized as follows. Section 2 presents the BWA system reference model. The design and implementation of the subscriber station MAC S/W is present section 3. Finally, we conclude with a summary in section 4. 2. SYSTEM REFERENCE MODEL WirelessMAN system supports the Medium access control protocol (MAC) and the Physical layer. This section overviews the technical medium access control and physical layer features based on IEEE 802.16. Figure 1 shows the WirelessMAN trial system reference model. Figure 1. BWA System Reference Model Data Payload MAC Frame/ Header process 0.5msec codewords Buffer Network Interface Task UL-MAP Codeword 1 Codeword 2 ...... Codeword N Data Payload 1 Data Payload 2 ........ Data Payload 8 M AC M essage Processor Msg Payload 1 Msg Payload 2 UCD/DCD process Ethernet Frame Ethernet Interface process