We consider a Gaussian interference channel with independent direct and cross link channel gains, each of which is independent and identically distributed across time. Each transmitter-receiver user pair aims to maximize its long-term average transmission rate subject to an average power constraint. We formulate a stochastic game for this system in three different scenarios. First, we assume that each user knows all direct and cross link channel gains. Later, we assume that each user knows channel gains of only the links that are incident on its receiver. Lastly, we assume that each user knows only its own direct link channel gain. In all cases, we formulate the problem of finding the Nash equilibrium as a variational inequality (VI) problem and present a novel heuristic for solving the VI. We also present a lower bound on the utility for each user at any Nash equilibrium in the case of the games with partial information. We obtain this lower bound using a water-filling like power allocation that requires only knowledge of the distribution of a user's own channel gains and average power constraints of all users.

The optimal power-delay tradeoff is studied for a time-slotted independently and identically distributed fading point-to-point link, with perfect channel state information at both transmitter and receiver, and with random packet arrivals to the transmitter queue. It is assumed that the transmitter can control the number of packets served by controlling the transmit power in the slot. The optimal tradeoff between average power and average delay is analyzed for stationary and monotone transmitter policies. For such policies, an asymptotic lower bound on the minimum average delay of the packets is obtained, when average transmitter power approaches the minimum average power required for transmitter queue stability. The asymptotic lower bound on the minimum average delay is obtained from geometric upper bounds on the stationary distribution of the queue length. This approach, which uses geometric upper bounds, also leads to an intuitive explanation of the asymptotic behavior of average delay. The asymptotic lower bounds, along with previously known asymptotic upper bounds, are used to identify three new cases where the order of the asymptotic behavior differs from that obtained from a previously considered approximate model, in which the transmit power is a strictly convex function of real valued service batch size for every fade state.

We study the tradeoff between the average error probability and the average queueing delay of messages which randomly arrive to the transmitter of a point-to-point discrete memoryless channel that uses variable rate fixed codeword length random coding. Bounds to the exponential decay rate of the average error probability with average queueing delay in the regime of large average delay are obtained. Upper and lower bounds to the optimal average delay for a given average error probability constraint are presented. We then formulate a constrained Markov decision problem for characterizing the rate of transmission as a function of queue size given an average error probability constraint. Using a Lagrange multiplier the constrained Markov decision problem is then converted to a problem of minimizing the average cost for a Markov decision problem. A simple heuristic policy is proposed which approximately achieves the optimal average cost.

We study a sensor node with an energy harvesting source. The generated energy can be stored in a buffer. The sensor node periodically senses a random field and generates a packet. These packets are stored in a queue and transmitted using the energy available at that time. We obtain energy management policies that are throughput optimal, i.e., the data queue stays stable for the largest possible data rate. Next we obtain energy management policies which minimize the mean delay in the queue. We also compare performance of several easily implementable sub-optimal energy management policies. A greedy policy is identified which, in low SNR regime, is throughput optimal and also minimizes mean delay.

We study a sensor node with an energy harvesting source. In any slot, the sensor node is in one of two modes: Wake or Sleep. The generated energy is stored in a buffer. The sensor node senses a random field and generates a packet when it is awake. These packets are stored in a queue and transmitted in the wake mode using the energy available in the energy buffer. We obtain energy management policies which minimize a linear combination of the mean queue length and the mean data loss rate. Then, we obtain two easily implementable suboptimal policies and compare their performance to that of the optimal policy. Next, we extend the Throughput Optimal policy developed in our previous work to sensors with two modes. Via this policy, we can increase the throughput substantially and stabilize the data queue by allowing the node to sleep in some slots and to drop some generated packets. This policy requires minimal statistical knowledge of the system. We also modify this policy to decrease the switching costs.

Average-delay optimal scheduling of messages arriving to the transmitter of a point-to-point channel is considered in this paper. We consider a discrete time batch-arrival batch-service queueing model for the communication scheme, with service time that may be a function of batch size. The question of delay optimality is addressed within the semi-Markov decision-theoretic framework. Approximations to the average-delay optimal policy are obtained.

We develop a multi-class discrete-time processor-sharing queueing model for scheduled message communication over a discrete memoryless degraded broadcast channel. The framework we consider here models both the random message arrivals and the subsequent reliable communication by suitably combining techniques from queueing theory and information theory. Requests for message transmissions are assumed to arrive according to i.i.d. arrival processes. Then, (i) we derive an outer bound to the stability region of message arrival rate vectors achievable by the class of stationary scheduling policies, (ii) we show for any message arrival rate vector that satisfies the outer bound, that there exists a stationary "state-independent" policy that results in a stable system for the corresponding message arrival processes, and (iii) under an asymptotic regime, we show that the stability region of information arrival rate vectors is the information-theoretic capacity region of a degraded broadcast channel.

The stability of scheduled multi-access communication with random coding and independent decoding of messages is investigated. The number of messages that may be scheduled for simultaneous transmission is limited to a given maximum value, and the channels from transmitters to receiver are quasistatic, flat, and have independent fades. Requests for message transmissions are assumed to arrive according to an i.i.d. arrival process. Then, we show the following: (1) in the limit of large message alphabet size, the stability region has an interference limited information-theoretic capacity interpretation, (2) state-independent scheduling policies achieve this asymptotic stability region, and (3) in the asymptotic limit corresponding to immediate access, the stability region for non-idling scheduling policies is shown to be identical irrespective of received signal powers

We model and analyse the stability of, the communication scheme. We obtain an arrival rate stability limit that is identical for all SNR distributions considered.

Two factors that need to be considered jointly in multi-access communications are: random arrival of messages for transmission and the noise and interference affecting the communication process. Telatar and Gallager (1995) and Telatar (1992) proposed a multi-access scheme over a no-fading AWGN channel and considered both these factors jointly. By formulating this scheme as a processor sharing queue with a single class of customers, the expected duration of signal (encoded messages) transmission for a given probability of decoding error was determined. Along similar lines, we analyse the multi-access scheme over flat slow fading channels and show that the multi-access scheme formulates as a processor sharing queueing system with multiple classes of customers with each customer belonging to a class determined by the SNR value at which it is received. The performance measures of interest in our study are: (a) the maximum stable throughput, and (b) the signaling duration for a tolerable message. We also conjecture the stability condition of the processor sharing queue. We simulate the scheme to obtain average delays over Rayleigh fading channels, Rician fading channels with Rician factors K=1 and K=1000 and no-fading AWGN channels. The results for the different fading channels are compared for equal values of average received SNR. We find that there is a threshold for the average received SNR, above which the average delay for the fading channel is less than that for the no-fading channel.

The scheduling of user-session transmission-priority time slots in time-periodic frames on links in a network is considered from an algorithmic standpoint. Priority slot schedules with low schedule delays can be used in a flow control scheme to lower limits on packet intranetwork delay. An NP-completeness result is proved, showing that for general networks the scheduling of priority slots to obtain a minimum sum of schedule delays is algorithmically hard. Minimum-delay scheduling algorithms for special classes and a scheduling heuristic for general networks are presented.>

We present two protocols for information exchange between multiple identical senders and a single receiver. At each instant, every sender sends one bit, and the bits from all of senders are or-ed together into one bit before being received by the receiver. If a sender has a data message to send, it sends the message bits one by one; otherwise it sends zero bits. Clearly, if the sending of two messages by two senders overlap, then the resulting “collision” can result in a corrupted message, i.e., one that was not sent by either sender. The function of the protocol is to deliver those and only those messages that are not corrupted by collision. (In other words, the receiver acts as a discriminating seine that catches and delivers only uncorrupted messages; hence the title.) The two protocols presented here are based on Manchester codes and general balanced codes, respectively.