This paper addresses the problem of frequency domain packet scheduling (FDPS) incorporating spatial division multiplexing (SDM) multiple input multiple output (MIMO) techniques on the 3GPP long term evolution (LTE) downlink. We impose the LTE MIMO constraint of selecting only one MIMO mode (spatial multiplexing or transmit diversity) per user per transmission time interval (TTI). First, we address the optimal MIMO mode selection (multiplexing or diversity) per user in each TTI in order to maximize the proportional fair (PF) criterion extended to frequency and spatial domains. We prove that the SU-MIMO (single-user MIMO) FDPS problem under the LTE requirement is NP-hard and therefore, we develop two approximation algorithms (one with full channel feedback and the other with partial channel feedback) with provable performance bounds. Based on 3GPP LTE system model simulations, the approximation algorithm with partial channel feedback is shown to have comparable performance to the one with full channel feedback, while significantly reducing the channel feedback overhead by nearly 50%.

In this paper, we analyze the asymptotic performance of multiple antenna channels where the transmitter has finite bit channel state information. Using the diversity multiplexing tradeoff to characterize the system performance, we demonstrate that channel feedback can fundamentally change the system behavior. Even one-bit of information can increase the diversity order of the system compared to the system with no transmitter information. In addition, as the amount of channel information at the transmitter increases, the diversity order for each multiplexing gain increases and goes to infinity for perfect transmitter information. The major reason for diversity order gain is in temporal power control, which adapts the power control strategy based on the average channel conditions of the channel.

Transmitter side information enables techniques such as beamforming, power control, and rate control in fading channels. It is commonly accepted in the literature that the addition of transmitter information (CSIT) to receiver information (CSIR) provides better performance than receiver information alone. In this work, we examine the performance of a symmetric, single-input, multiple-output (SIMO) channel in which CSIT is acquired through the use of training symbols, and we have a genie-aided receiver. We give a closed form expression for outage probability at high SNR while accounting for the resources consumed by training. We also analyze the diversity-multiplexing tradeoff and find that, though the diversity falls far below that of systems with perfect CSIT, it is still sufficiently superior to that achieved by CSIR-only systems to justify the cost of training. We show that, at zero multiplexing, transmitter training doubles the diversity order of a CSIR-only system and offers nonzero diversity at all achievable multiplexing gains

We consider a multiple antenna system with finite rate feedback, in which the quantized channel state information at the transmitter is used solely for temporal power control. We show that similar to systems without feedback, the tradeoff between diversity order and multiplexing gain exists. However, unlike the systems with feedback that apply both rate and power control, systems with only power control are unable of achieving non-zero diversity order at the maximum multiplexing gain. The analysis is based on asymptotic behavior of the distribution of order statistics of the eigenvalues of channel matrix, which is a key step in evaluating the diversity order.

In this paper, we study the impact of delay constraints on the throughput of a queued multiple-access system. We model the channel as a collision channel with carrier sense to capture the inherent information sharing due to broadcast nature of the wireless channels. Since the queue state information is unknown to other nodes and a delay-bounded communication is desired, we show that a fraction of throughput is lost as protocol overhead. More importantly, we show that there is a tradeoff between protocol overhead and queuing delay; larger delays allowing smaller overheads. In addition, we show that larger network loads can also be used to reduce protocol overhead, which is in direct contrast of the behavior exhibited by commonly used medium access protocols

In this paper, we analyze the outage probability of a single user system with multiple antennas at the transmitter, single antenna at the receiver, and finite rate feedback power control. The optimum power control is complex and the analysis is not tractable. Hence we propose a sub-optimal power allocation scheme, with very low computational complexity, which is asymptotically optimum. Analyzing the proposed algorithm we show that the diversity order can potentially be increased unboundedly by increasing the feedback rate and without increasing number of transmit or receive antennas. We find a closed form approximation to this diversity-like gain at large SNRs, as a function of number of transmit antennas, number of quantization levels, and average available SNR. Simulation results confirm the validity of the analysis.