**2. User based bandwidth allocation**

IEEE 802.16 (WiMAX) provides differentiated Quality of Service (QoS) (IEEE 802.16 2004) (IEEE 802.16e 2005) (Vaughan-Nichols 2004). This is achieved by having five different types of service classes. Each of these service classes caters to specific type of data. Unsolicited Grant Services (UGS) supports real time data streams that generate fixed size packets at periodic intervals. For example Voice over IP without silence suppression, T1/E1. Extended Real Time Polling Services (eRTPS) is designed to support real-time service flows that generate variable sized data packets on periodic basis, like VoIP with silence suppression. Real Time Polling Services (RTPS) supports real time data streams that generate variable size packets on periodic basis. For example Multimedia formats like an MPEG video. Non Real Time Polling Services (nRTPS) supports delay tolerant data streams generating variable size data packets, like FTP. Best Effort(BE) supports data streams which do not require any service level. Ex Web browsing, Email etc.

User keeps generating the data. This data gets queued into one of the five service classes based on the type of data and the quality of service requirements for the data. Once the data gets queued, the device needs to request for bandwidth so that the data packets can be transmitted. Classically, the widely used bandwidth allocation algorithms have followed contention based logic. The device contends for the wireless medium. If no other device is contending for the bandwidth then the device transmits the data. Algorithms like ALOHA, Slotted ALOHA, CSMA, CSMA-CD use contention based bandwidth allocation. Even IEEE 802.11 (Wi-Fi) uses contention based bandwidth allocation mechanism called CSMA-CA.

WiMAX supports demand based bandwidth allocation mechanism. Each Mobile Station (MS) is allocated small amount of bandwidth that is used by the MS to request for additional bandwidth. Based on the availability of bandwidth and the type of service requesting for bandwidth, the Base Station (BS) allocates bandwidth. MS requests bandwidth on a per service class basis and the BS allocates bandwidth on a per-SS basis. Various types of contention based bandwidth request/allocation mechanisms have been proposed in WiMAX. Aggregate bandwidth request mechanism is proposed in (Tao & Gani, 2009). Instead of sending separate bandwidth request for each service class, a single request is sent. Service class bandwidth allocation is proposed in (Wee & Lee, 2009). Delay intolerant service classes are provided bandwidth on priority. Subsequently delay tolerant service classes are allocated bandwidth. Adaptive bandwidth request scheme is proposed in (Liu & chen, 2008). Contention free bandwidth request opportunities are provided within the contention based request opportunities for some SS. Predictive bandwidth allocation algorithm is proposed in (Peng et. al, 2007). Based on the current arrival pattern, bandwidth is requested beforehand for future packets. Channel aware bandwidth allocation algorithm is proposed in (Lin et. al, 2008). Another form of adaptive bandwidth allocation algorithm is proposed in (Chiang et. al, 2007). The TDD frame is dynamically adjusted based on the amount of uplink and downlink data. In (Park, 2009) bandwidth request algorithm is proposed that takes both the current size of the queue and the deadline assigned to each packet. CDMA bandwidth request code based bandwidth allocation mechanism is proposed in (Lee et. al, 2010). The CDMA bandwidth request code is chosen randomly, but in (Lee et. al, 2010) the bandwidth request code is intelligently chosen so that the code itself indicates the amount of bandwidth needed by the MS. This reduces the number of control message transactions between the MS and SS. In (Rong et al, 2007) two algorithms are proposed namely adaptive power allocation (APA) and call admission control (CAC). The two algorithms work in tandem to allocate bandwidth to the MS.

All the algorithms proposed above are service class based bandwidth request/allocation algorithms. MS shall send bandwidth request for all its service classes. Bandwidth is then allocated based on the service class. All UGS service classes from different users are allocated bandwidth first then the RTPS service flows are allocated bandwidth followed by eRTPS. Next, the delay tolerant service class nRTPS is allocated bandwidth. Finally BE service class is allocated bandwidth. This method of bandwidth allocation treats all MS alike. If there are 10 MS in the network and if all of them are generating BE traffic then all the BE service classes are allocated bandwidth on a first come first serve basis. Of these 10 users, there may be some users who may wish to pay more if their BE traffic is treated on priority. So, users can be segregated into different groups and bandwidth can be allotted to the users based on the group to which they belong to. In this section we shall explore three user based bandwidth allocation algorithms. Fig. 1 shows service class based bandwidth allocation mechanism.

gets queued, the device needs to request for bandwidth so that the data packets can be transmitted. Classically, the widely used bandwidth allocation algorithms have followed contention based logic. The device contends for the wireless medium. If no other device is contending for the bandwidth then the device transmits the data. Algorithms like ALOHA, Slotted ALOHA, CSMA, CSMA-CD use contention based bandwidth allocation. Even IEEE 802.11 (Wi-Fi) uses contention based bandwidth allocation mechanism called CSMA-CA.

WiMAX supports demand based bandwidth allocation mechanism. Each Mobile Station (MS) is allocated small amount of bandwidth that is used by the MS to request for additional bandwidth. Based on the availability of bandwidth and the type of service requesting for bandwidth, the Base Station (BS) allocates bandwidth. MS requests bandwidth on a per service class basis and the BS allocates bandwidth on a per-SS basis. Various types of contention based bandwidth request/allocation mechanisms have been proposed in WiMAX. Aggregate bandwidth request mechanism is proposed in (Tao & Gani, 2009). Instead of sending separate bandwidth request for each service class, a single request is sent. Service class bandwidth allocation is proposed in (Wee & Lee, 2009). Delay intolerant service classes are provided bandwidth on priority. Subsequently delay tolerant service classes are allocated bandwidth. Adaptive bandwidth request scheme is proposed in (Liu & chen, 2008). Contention free bandwidth request opportunities are provided within the contention based request opportunities for some SS. Predictive bandwidth allocation algorithm is proposed in (Peng et. al, 2007). Based on the current arrival pattern, bandwidth is requested beforehand for future packets. Channel aware bandwidth allocation algorithm is proposed in (Lin et. al, 2008). Another form of adaptive bandwidth allocation algorithm is proposed in (Chiang et. al, 2007). The TDD frame is dynamically adjusted based on the amount of uplink and downlink data. In (Park, 2009) bandwidth request algorithm is proposed that takes both the current size of the queue and the deadline assigned to each packet. CDMA bandwidth request code based bandwidth allocation mechanism is proposed in (Lee et. al, 2010). The CDMA bandwidth request code is chosen randomly, but in (Lee et. al, 2010) the bandwidth request code is intelligently chosen so that the code itself indicates the amount of bandwidth needed by the MS. This reduces the number of control message transactions between the MS and SS. In (Rong et al, 2007) two algorithms are proposed namely adaptive power allocation (APA) and call admission control (CAC). The two

All the algorithms proposed above are service class based bandwidth request/allocation algorithms. MS shall send bandwidth request for all its service classes. Bandwidth is then allocated based on the service class. All UGS service classes from different users are allocated bandwidth first then the RTPS service flows are allocated bandwidth followed by eRTPS. Next, the delay tolerant service class nRTPS is allocated bandwidth. Finally BE service class is allocated bandwidth. This method of bandwidth allocation treats all MS alike. If there are 10 MS in the network and if all of them are generating BE traffic then all the BE service classes are allocated bandwidth on a first come first serve basis. Of these 10 users, there may be some users who may wish to pay more if their BE traffic is treated on priority. So, users can be segregated into different groups and bandwidth can be allotted to the users based on the group to which they belong to. In this section we shall explore three user based bandwidth allocation algorithms. Fig. 1 shows service class based

algorithms work in tandem to allocate bandwidth to the MS.

bandwidth allocation mechanism.

Fig. 1. Service class based bandwidth allocation mechanism.
