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Abstract-We consider a centralized Spectrum Server that coordinates the transmissions of a group of links sharing a common spectrum. Links employ on-off modulation with fixed transmit power when active. In the on state, a link obtains a data rate determined by the signal-to-interference ratio on the link. With knowledge of the link gains in the network, the spectrum server schedules the on/off periods of the links so as to satisfy constraints on link fairness and efficiency. We express fairness constraints as lower bounds on the average minimum rate for each link. Efficiency constraints are expressed as lower bounds on the ratio of the average rate to the average transmit power for each link. Subject to fairness and efficiency constraints, the spectrum server finds a schedule that maximizes the average sum rate. Using a graph theoretic model for the network and a linear programming formulation, the resulting schedules are a collection of time shared transmission modes (sets of active links). In the special case when there is no minimum rate constraint, varying the efficiency constraint can cause the optimal policy to vary from a fixed dominant mode with highest sum rate being operated all the time to time sharing among singleton modes in which just one link is active. We also address the case of maximum common rate scheduling under efficiency constraints. Simulation results are presented to substantiate our findings.

Abstract-We evaluate the peak and average power savings due to relay deployments in cellular systems via a simulation study. The peak power savings translate to cost reduction in power amplifiers. The average power savings lead to savings in electricity bills. Half-duplex relays are placed one per sector in a 19-cell, 57-sector cellular network. In the baseline case, the base stations control their transmit powers to achieve a common rate among users. When relays are present in the system, optimal powers are found when the relays get the complete message to be relayed to the user. The codebooks at the relays are chosen such that the users obtain a rate corresponding to the sum of the received powers from the base station and the relay. We observe that when power control is employed, the peak power saving is 2.6 dB and the average total power in the system can be reduced by 3 dB.

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With the explosive and sustained growth of data usage on both 3G and 4G mobile broadband wireless networks, new techniques need to be found to deliver data to end users efficiently. One of the key drivers of that data demand is video. Evolved Multimedia Broadcast Multicast Service (eMBMS) is one technique in Long Term Evolution (LTE) that provides a broadcast bearer to deliver video content and file delivery to an unlimited number of users. This bearer makes use of multiple cell sites to build a “single frequency network” (SFN) zone with identical downlink transmission over part of the LTE Orthogonal Frequency Division Multiplexing (OFDM) waveform. The resulting signal is combined at the user equipment's antenna in such a way that what is normally a neighboring cell site contributing interference becomes the source of a useful signal, thus improving the overall information signal to interference ratio, as well as spectral efficiency. In this paper, eMBMS technology and architecture are presented along with estimates of achieved performance and the impact on radio network engineering. We conclude that while eMBMS may not be an efficient solution to offer nationwide contiguous services throughout a mobile network, it may be efficiently used across an entire metropolitan area and the surrounding “capacity limited” rural areas when using a low radio band such as 700 MHz or 800 MHz, offering an impressive spectral efficiency of 1.5 b/s/Hz. © 2013 Alcatel‐Lucent.