In this paper, we propose Transmission Control Protocol (TCP)-aware cross layer scheduling algorithms in a multipoint-to-point network such as the uplink of an IEEE 802.16 (WiMAX) network. Inadequate bandwidth allocation to a TCP flow may lead to timeout and since TCP source drops its congestion window ( @math ) immediately after a timeout, it may affect the average throughput adversely. On the other hand, since the TCP source increases its @math only linearly upon the availability of bandwidth, any excess assignment of bandwidth may remain underutilized. The proposed scheduling algorithms address this by allocating the resources based on @math and TCP timeout. Moreover, since we focus on uplink scheduling, we consider that only flow level resource requirement is communicated to the Base Station ( @math ) instead of per packet information. The schedulers also take into account the wireless channel characteristics and are thus cross layer in nature. Through exhaustive simulations, we demonstrate that the proposed schedulers exhibit enhanced throughput and fairness properties when compared to that of Round Robin (RR) scheduler under different shadowing. We demonstrate a gain between 3.5 to 15 in throughput and 15 to 25 in channel utilization over RR scheduler under different shadowing.
Point-to-multipoint broadband wireless access (BWA) is an attractive solution to provide advanced data services to users who do not have easy access to wireline data services. However, BWA will need to support delay sensitive services as users and applications are becoming increasingly sophisticated. Wireless packet scheduling is an important part of quality-of-service (QoS) provisioning in BWA. The biggest difficulty in wireless packet scheduling is the location-dependent channel errors. Channel condition independent fair scheme (CIF) (T.S. Eugene, et al, March 1998) uses explicit leading lagging approach to compensate for the erroneous channel state, but is not able to satisfy both rapid convergent guaranteed throughput and fairness. In this paper, we propose to use the token bank fair queuing (TBFQ) scheduling algorithm as a QoS provisioning mechanism for an asymmetric broadband point-to-multipoint wireless LAN. We consider the throughput and fairness performance of TBFQ under location-dependent channel error condition with variable packet length. This work is an extension of our previous work in applying TBFQ in next generation cellular networks. A fundamental problem in networking is the allocation of limited resources among the users of the network. In a traditional layered network architecture, the resource to be allocated at the medium access control (MAC) and network layers utilizes communication links, viewed as "bit pipes" that deliver data at a fixed rate with occasional random errors. Though this separation has many advantages, there is a growing awareness that this simple bit-pipe view is inadequate, particularly in the context of modern wireless data networks. In this article, several basic cross-layer resource allocation problems for wireless fading channels are considered. The article focuses on the characterization of fundamental performance limits while taking into account both network layer QoS and physical layer performance. SUMMARY The token bank fair queuing algorithm (TBFQ) is a novel scheduling algorithm that is suitable for wireless multimedia services. The bandwidth allocation mechanism integrates the leaky bucket structure with priority handling to address the problem of providing quality-of-service (QoS) guarantees to heterogeneous applications in the next generation packet-switched wireless networks. Scheduling algorithms are often tightly integrated with the wireless medium access control (MAC) protocol. However, when heterogeneous wireless systems need to be integrated and interoperate with each other, it is desirable from the QoS provisioning standpoint to decouple scheduling algorithm from the MAC protocol. In this paper we propose a framework of seamless QoS provisioning and the application of TBFQ for uplink and downlink scheduling in wireless networks. We study its performance under a generic medium access framework that enables the algorithm to be generalized to provide QoS guarantees under various medium access schemes. We give a brief analysis of the algorithm and compare its performance with common scheduling algorithms through simulation. Our results demonstrate that TBFQ significantly increases wireless channel utilization while maintaining the same QoS, unlike many fair queuing algorithms, TBFQ does not require timestamping information of each packet arrival an impractical feature in an already resource scarce environment. This makes TBFQ suitable for wireless multimedia communication. Copyright # 2004 John Wiley & Sons, Ltd.