We consider the allocation of spectral and power resources every subframe (1 ms) on the uplink of the Long Term Evolution (LTE) wideband orthogonal frequency division multiple access (OFDMA) cellular network. System bandwidth is divided into multiple sub-bands. The fractional power control to manage interference is allowed to be sub-band dependent. Moreover, the channel gains from the base-station to the mobiles (user equipment (UE) in LTE) can vary with the sub-band. The power and spectral resources are to be allocated among different UEs in a cell based on channel conditions, desired fairness/QoS, and constraints on power due to interference and power limitation at a UE. For N UEs and M sub-bands, we exploit the structure of the underlying optimization problem to obtain an interior point method for optimal resource allocation where each Newton step has complexity O(NM). To implement this in an OFDMA system, we delineate a simple control signalling structure where the UE computes in O(M) time a waterfllling solution every subframe it is assigned resources. When the allocation is restricted to contiguous allocation in frequency due to single carrier constraint in LTE, we convert the solution computed above into a feasible solution in O(NM) time. For typical network scenarios, the solution thus computed is numerically shown to be very close to the optimal solution without the contiguous constraint.

In recent years, M2M (machine to machine) communications has increasingly been seen as a new growth area for wide-area wireless technologies which were designed for voice and high-speed packet data applications. In this paper, we use simulations to estimate the capacity of M2M applications over one of the widely used 3G wireless systems, CDMA2000 1x. We present capacity estimates of the CDMA2000 1x system for applications such as SMS, smart grid and vehicle tracking, under different network loading conditions. Our simulations show that the capacity of the aforementioned applications is reverse-link limited. In particular, the most commonly used configuration of reverse access channel in existing networks severely limits the M2M capacity. With better network configuration, use of enhanced access channel, and reverse link interference cancellation, the M2M capacity can be significantly improved. Our simulations show that the SMS capacity over 1x can reach about 2,400 SMS's per minute per sector on a single CDMA2000 1x carrier. In addition, the optimized network can support 56,000 smart-grid node or track approximately 2,900 vehicles per sector per 1.25MHz.

We introduce the concept of a fiber aided wireless network architecture (FAWNA), which allows high-speed mobile connectivity by leveraging the speed of optical networks. Specifically, we consider a single-input, multiple-output (SIMO) FAWNA, which consists of a SIMO wireless channel interfaced with an optical fiber channel through wireless-optical interfaces. We propose a design where the received wireless signal at each interface is sampled and quantized before being sent over the fiber. The capacity of our scheme approaches the capacity of the architecture, exponentially with fiber capacity. We also show that for a given fiber capacity, there is an optimal operating wireless bandwidth and number of interfaces. We show that the optimal way to divide the fiber capacity among the interfaces is to ensure that each interface gets enough rate so that its noise is dominated by front end noise rather than by quantizer distortion. We also show that rather than dynamically change rate allocation based on channel state, a less complex, fixed rate allocation scheme can be adopted with very small loss in performance.

We consider a multiple-input multiple-output (MIMO) wideband Rayleigh block-fading channel where the channel state is unknown to both the transmitter and the receiver and there is only an average power constraint on the input. We compute the capacity and analyze its dependence on coherence length, number of antennas and receive signal-to-noise ratio (SNR) per degree of freedom. We establish conditions on the coherence length and number of antennas for the noncoherent channel to have a “near-coherent” performance in the wideband regime. We also propose a signaling scheme that is near-capacity achieving in this regime. We compute the error probability for this wideband noncoherent MIMO channel and study its dependence on SNR, number of transmit and receive antennas and coherence length. We show that error probability decays inversely with coherence length and exponentially with the product of the number of transmit and receive antennas. Moreover, channel outage dominates error probability in the wideband regime. We also show that the critical as well as cutoff rates are much smaller than channel capacity in this regime.

We consider the problem of jamming in non-coherent wideband fading channels. While the problem is well understood for coherent channels, the results for the coherent case do not generalize in the non-coherent regime. We show that energy-limited jammers do not affect capacity in the wideband regime. We also propose a training based transmission scheme that is able to achieve the wideband limit in the presence of a jammer

We consider a multiple-input, multiple-output (MIMO) wideband Rayleigh block fading channel where the channel state is unknown to both the transmitter and the receiver and there is only an average power constraint on the input. We compute the error probability and study its dependence on receive signal-to-noise ratio (SNR), number of transmit and receive antennas and coherence length. We show that error probability decays inversely with coherence length and exponentially with the product of the number of transmit and receive antennas. Moreover, channel outage dominates error probability in the wideband regime. We also show that the critical as well as cut-off rates are much smaller than channel capacity in this regime

The concept of a fiber aided wireless network architecture (FAWNA) is introduced in [Ray et al., Allerton Conference 2005], which allows high-speed mobile connectivity by leveraging the speed of optical networks. In this paper, we consider a single-input, multiple-output (SIMO) FAWNA, which consists of a SIMO wireless channel and an optical fiber channel, connected through wireless-optical interfaces. We propose a scheme where the received wireless signal at each interface is quantized and sent over the fiber. Though our architecture is similar to that of the classical CEO problem, our problem is different from it. We show that the capacity of our scheme approaches the capacity of the architecture, exponentially with fiber capacity. We also show that for a given fiber capacity, there is an optimal operating wireless bandwidth and an optimal number of wireless-optical interfaces. The wireless-optical interfaces of our scheme have low complexity and do not require knowledge of the transmitter code book. They are also extendable to FAWNAs with large number of transmitters and interfaces and, offer adaptability to variable rates, changing channel conditions and node positions

We consider a multiple-input, multiple-output (MIMO) wideband Rayleigh block fading channel, where the channel state is unknown to both the transmitter and the receiver. With only an average power constraint, we compute the capacity of this channel and consider its interaction with the coherence length, number of transmit and receive antennas and receive signal-to-noise ratio (SNR) per degree of freedom. We establish how large the coherence length has to be in order for the non-coherent channel to have a "near coherent" performance in the wideband regime. More specifically, we show that if the coherence length of the channel is above a certain SNR (bandwidth) dependent threshold, the non-coherent and coherent capacities are the same in the large bandwidth regime. We also propose a signaling scheme that is near-optimal in the wideband regime

A two transmitter single receiver multiple access noise-free network is considered where interference is additive and the transmit and receive alphabet size is the same. We consider two performance metrics - code rate and sum rate. Code rate is defined as the ratio of the symbols recovered, after multiple access interference, to the symbols sent by the transmitters. The sum rate is the number of symbols successfully received per unit time. A packet by packet coding scheme is presented where we determine how these rates change with redundancy. We propose a coding mechanism that maximizes the code and sum rates and show that it suffices to code at only one of the transmitters and that systematic codes are sufficient for this purpose. The development is independent of the alphabet size the symbols are defined over. We also show that we can achieve maximum rates by using a random code. This allows us to choose codes in a random fashion and the scheme achieves optimality with probability tending to 1 exponentially with the code length.