An important application for the IEEE 802.16 technology (also called WiMAX) it to provide high-speed access to the Internet where the transmission control protocol (TCP) is the core transport protocol. In this paper we study through extensive simulation scenarios, the performance characteristics of five representative TCP schemes, namely TCP New Reno, Vegas, Veno, Westwood and BIC, in WiMAX networks, under the conditions of correlated wireless errors, asymmetric end-to-end capabilities and link congestion. The target is to evaluate how the above conditions would affect the TCP congestion control, and suggest the best schemes to be employed in WiMAX Networks.

Broadband wireless access (BWA) offers attractive features such as ease and speed of deployment, fast realization of revenues, and low infrastructure cost. This paper focuses on medium access control (MAC) alternatives that can find application in an LMDS/LMCS network capable of supporting multimedia traffic. Multifrequency demand assignment TDMA-based schemes appear (at the moment) to be a suitable choice in this context. The selected protocol should be dynamically capable of providing multirate capabilities and quality-of-service guarantees. An obvious candidate for the aforementioned purpose is the LMDS-specific MAC proposal in the DAVIC 1.2 recommendation. For purposes of comparison, we also examine the evolving IEEE 802.14 MAC convergence protocol and MCNS (multimedia cable network system) DOCSIS (ITU J-112) MAC standard that are intended to support similar applications and services in an HFC (hybrid fiber coax) environment. The three protocols are examined under noiseless and noisy channel conditions. Previous results on LMDS channel characteristics are summarized and used for modeling noisy channel conditions. The candidate protocols are compared in terms of mean access delay, throughput, and collision multiplicity statistics, when contention of users is involved. The effect of dynamic slot allocation on the performance of the candidate protocols is also examined.

This paper focuses on medium access control (MAC) alternatives that can find application in a LMDS/LMCS network capable of supporting multimedia traffic. Multi-frequency, demand assignment TDMA-based schemes appear at the moment to be a suitable choice in this context. The selected protocol should be dynamically capable of provision of multirate capabilities and quality of service guarantees. An obvious candidate for the above purpose is the LMDS-specific MAC proposal in the DAVIC 1.2 recommendation. For purposes of comparison, we also examine the evolving IEEE 802.14 MAC convergence protocol that is intended to support similar applications and services in an HFC (hybrid fiber coax) environment. The MCNS (multimedia cable network system) MAC characteristics are also briefly described.

The comparative performance of a number of reservation-based bandwidth sharing policies that could be used to maximize the link utilization and/or offer equally fair or preferential treatment to a class of supported users, is examined in the context of a radio asynchronous transfer mode local-area network (ATM LAN). Our analytical results, based an a recursion for the link occupancy distribution originally suggested by Kaufman (1981) and Roberts (1981) independently and subsequently extended to include finite source population models, are further extended in the cases of equal sharing of the resources with retries, and a dynamic sharing mechanism in which, when the available capacity is exceeded, weighted reductions for the active users' rates and queueing are employed. Next, examining the application of the above sharing schemes in an indoor radio environment, we apply switched diversity and a Reed-Solomon-based forward error correction (FEC) scheme to recover radio-related (Rayleigh fading) packet losses. The performance and the effects of the fading-mitigating switched-antenna-diversity mechanism and the required on a packet-basis coding protection are taken into account in order to establish the actual radio link throughput under the above conditions.

A first assessment of the applicability and the tradeoffs involved in a switched (antenna) diversity approach is presented here as seen in the context of a future indoor wireless network operating in the mm-wavelength radio spectrum targeted to provide radio access to asynchronous transfer mode local area networks (ATM LAN's) and broadband integrated services digital networks (B-ISDN). Measurements conducted at 21.6 GHz are used to examine the gain variation of switched-diversity alternatives in terms of cumulative distribution functions. The performance of a two-branch post-detection code diversity combining scheme under Rayleigh fading conditions is also included for purposes of comparison. The results of our work here confirm the hypothesis that the choice of the employed antenna diversity technique in combination with the selected micro-cellular architecture have significant effects on both the throughput and the measured performance of future radio links.

A lbrst assessment of the applicability and the trade- offs involved in a switched (antenna) diversity approach is pre- sented here as seen in the context of a future indoor wireless network operating in the mm-wavelength radio spectrum tar- geted to provitde radio access to asynchronous transfer mode local area networks (ATM LAN's) and broadband integrated services digital networks (B-ISDN). Measurements conducted at 21.6 GHz are used to examine the gain variation of switched- diversity alternatives in terms of cumulative distribution func- tions. The performance of a two-branch post-detection code diversity combining scheme under Rayleigh fading conditions is also included for purposes of comparison. The results of our work here confiirm the hypothesis that the choice of the employed antenna divers,ity technique in combination with the selected micro-cellular architecture have significant effects on both the throughput and the measured performance of future radio links.

Broadband optical networks which carry a wide range of traffic classes in an integrated fashion are considered. The focus is on so-called stream traffic in which each class if allocated different quantities of broadband for the duration of a call on an equal sharing policy. An exact analysis of the blocking conditions experienced by different classes of traffic demanding transmission through a network with the star or the ring topology is presented. Thus, blocking probabilities on tandem links are calculated by means of a recursive relation that considerably simplifies the complexity of the problem without ignoring the interdependencies among links. Being a solution to a multiple-classes-multiple-links blocking problem, the present work is a multidimensional generalization of a well-known analysis for a single trunk. The efficiency of the solution results from the linearity of the necessary computations.>

Broadband optical networks which carry a wide range of traffic classes in an integrated fashion are considered. The focus is on so-called stream traffic in which each class is allocated different quantities of bandwidth for the duration of a call. An exact analysis of the blocking conditions experienced by different classes of traffic demanding transmission through an N/sub 1/*N/sub 0/ switch is presented. No particular structure is assumed for the switch besides its capability of resolving output port contention by rearranging the input traffic. A two-dimensional generalization of an analysis for a single trunk is considered. Its efficiency rests on the linearity of the necessary computations, thus the relative independence from the dimensionality of the switch.>