We present an overview of the MAC and PHY layer enhancements required to ensure high application layer throughput for IEEE 802.11n. We describe an enhanced scheduled mode operation which is shown, through simulation, to yield an application layer throughput that is greater than 100 Mb/s in practical scenarios. We also demonstrate that the proposed enhancements significantly improve the application layer throughput with EDCA.

The paper presents a performance study of two algorithms for dynamic allocation of the dedicated channels (DCH) in UMTS over the air interface, namely least recently used (LRU) algorithm and an adaptive algorithm. The algorithms are designed to efficiently share the dedicated channels among users whose traffic patterns are characterized by bursty packet transfers followed by long inactivity periods. Specifically, Web browsing, FTP and email applications were considered in order to evaluate the performance of the above mentioned resource allocation algorithms in the context of bursty traffic with relaxed delay constraints and In the presence of delays introduced by the backhaul network

Universal Mobile Telecommunications System (UMTS) networks are capable of serving packet-switched data applications at bit rates as high as 384 kbps. This paper studies the capacity and utilization of the downlink of the Iub interface, which lies between the radio network controller (RNC) and the base station (NodeB) in the UMTS network. The 3GPP standards define a Node B "receive window" within which a frame should arrive for it to be processed and transmitted to the UE in time. If the frame arrives too late, it will be discarded. Such frame discard event results in some loss in voice/data quality. Via simulations, we evaluate the link capacity for web-browsing traffic at 64 kbps, 128 kbps and 384 kbps, with a frame discard probability target of 0.5%. Our results indicate that the Iub link utilization is very poor due to the highly bursty nature of data traffic. In order to alleviate this problem, we introduce a rate control (RC) scheme where the peak user data rate is temporarily lowered during times of high congestion. This lowering of data rate is done through appropriate selection of the transport block size within the transport format set. As a result of such rate control, the capacity of the Iub link improves.

Universal Mobile Telecommunication System (UMTS) networks are capable of serving packet-switched data applications at bit rates as high as 384 kbps. Multiplexing multiple data sessions in the radio access networks (RAN) of a UMTS network brings a tremendous capacity gain with respect to the circuit-switched networks, however the utilization of resources are very low due to the bursty nature of data traffic. This paper studies the capacity and utilization of the downlink of the Iub interface, which lies between the radio network controller (RNC) and the base station (NodeB) in a UMTS network. In earlier work, we presented simulation results that indicate that the Iub link utilization is very low with bursty web browsing data especially if each data user is allowed to peak at 384 kbps. Thus, we introduced a rate control algorithm by which the MAC layer constrains the peak rate of a user based on current load conditions. In this paper, we extend that study to the case where multiple service classes (64, 128 and 384 kbps) are multiplexed on the same Iub link. There are some fundamental differences between the ways it is implemented in the multi-service case. We tested the multiservice rate control algorithm with some mixed service scenarios where we noted significant increase in capacity.

We develop a new class of asynchronous distributed algorithms for the explicit rate control of elastic sessions in an integrated packet network. Sessions can request for minimum guaranteed rate allocations (e.g., minimum cell rates in the ATM context), and, under this constraint, we seek to allocate the max-min fair rates to the sessions. We capture the integrated network context by permitting the link bandwidths available to elastic sessions to be stochastically time varying. The available capacity of each link is viewed as some statistic of this stochastic process [e.g., a fraction of the mean, or a large deviations-based equivalent service capacity (ESC)]. The ESC is obtained so as to satisfy an overflow probability constraint on the buffer length. For fixed available capacity at each link, we show that the vector of max-min fair rates can be computed from the root of a certain vector equation. A distributed asynchronous stochastic approximation technique is then used to develop a provably convergent distributed algorithm for obtaining the root of the equation, even when the link flows and the available capacities are obtained from on-line measurements. The switch algorithm does not require per connection monitoring, nor does it require per connection marking of control packets. A virtual buffer based approach for on-line estimation of the ESC is utilized. We also propose techniques for handling large variations in the available capacity owing to the arrivals or departures of CBR/VBR sessions. Finally, simulation results are provided to demonstrate the performance of this class of algorithms in the local and wide area network context.

The available bit rate (ABR) sessions in an ATM network share the bandwidth left over after guaranteeing service to constant bit rate (CBR) and variable bit rate (VBR) traffic. Hence the bandwidth available to ABR sessions is randomly varying. This bandwidth must be shared by the sessions in a max-min fair fashion. Our point of departure in this paper is to formulate the problem of determining the max-min fair session rates as the problem of finding the root of a certain nonlinear vector equation; the same formulation also arises with our notion of max-min fairness with positive minimum cell rates (MCRs). This formulation allows us to use a stochastic approximation algorithm for online distributed computation of the max-min fair rates. We use the well known ordinary differential equation technique to prove convergence of the algorithm in the synchronous update case. We provide simulation results using the NIST simulator to show that the algorithm is able to track the max-min fair rates for slowly varying random available link bandwidths.