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This work investigates the energy efficiency of Recursive Least Square (RLS) beamforming algorithm by developing a new energy model, which is a function of beam width, range, instantaneous signal to noise plus interference ratio (SNIR) and inter element spacing. It analyzes the effect of varying inter element spacing on linear array geometry for energy efficient beam formation. We evaluated the amount...
Cognitive radio (CR) technology has attracted dramatic attentions recently because it has an ability to dynamically adapt to local spectrum availability and improves the radio spectrum utilization. In this paper, we propose a channel allocation algorithm where the base station allocates a channel to the secondary user by using the primary user arrival pattern. The proposed scheme selects a channel...
We propose a new limited feedback scheme for the downlink of multiuser MIMO OFDM systems based on fixed linear beamforming, i.e. the linear beamforming vectors are chosen from a fixed transmit codebook. The proposed feedback method allows the base station to uniformly approximate all multiuser rates for any selection of users and any combination of beamforming vectors defined by the transmit codebook;...
In this paper, a distributed power control algorithm is proposed to perform adaptive spatial multiplexing for the relay enhanced orthogonal frequency division multiple access (OFDMA) cellular systems. As the optimal spatial multiplexing problem is non-convex, we utilize the distributed iteration method to achieve its near-optimal solution. By determining the restriction on the transmit power for each...
An improved multiuser scheduling scheme which can reduce feedback load and preserve most of the capacity performance in MIMO channels is proposed in this paper. Each user compares its maximum SINR to a threshold and only those who fall above it along with the index transmit antenna are sent back to the base station. The base station allocates independent channels to the users with the highest SINR...
In this paper we consider a centralized cross-layer splitting algorithm of a multi-packet reception slotted ALOHA system for contention resolution. In the algorithm, a base station estimates the number of backlogged mobile terminals by using a first-order auto-regressive (AR) model based on the number of packets successfully transmitted over previous contention resolution intervals (CRIs). Estimation...
The channel assignment problem arises in a mobile communication network whenever there is an installation of a new base station or one cell is split into two or more cells or power of the base station is changed. Channel assignment or reassignment is an NP-hard problem and generally a heuristic approach is used for solving large sized problems. We have developed a ??copy best available?? heuristic...
In cognitive radio cellular networks (CogCell), the secondary users (SUs) can be admitted to the base station (BS) provided that the interferences to the primary users (PUs) are no higher than the pre-defined thresholds. In addition, different SUs may make different payments and require different quality of service (QoS). In this paper, we investigate the maximally achievable revenue obtained from...
This paper studies the optimal resource allocation problem for the relay-assisted orthogonal frequency-division multiple-access (OFDMA) -based multiuser system. A new transmission protocol, named hierarchical OFDMA, is proposed to support two-way transmissions between the base station (BS) and each mobile user (MU) with or without an assisting relay station (RS) in "relay" or "direct"...
To support dynamic traffic-asymmetry property in future wireless communication systems, we propose a hybrid- TDD scheme, combination of static-TDD and dynamic-TDD. By using adaptive power control, inner/outer scheduling and hybrid-link for guaranteeing safe downlink/uplink time-slots, we can effectively solve the interference problems of the dynamic- TDD scheme. Especially, an adaptive downlink power...
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