Communication channel

About: Communication channel is a research topic. Over the lifetime, 137411 publications have been published within this topic receiving 1715077 citations. The topic is also known as: communication channel & communications channel.

Beamspace MIMO for high-dimensional multiuser communication at millimeter-wave frequencies

Abstract: Millimeter-wave (mm-wave) systems operating from 30–300GHz provide a unique opportunity for meeting the exploding capacity demands on wireless networks. In addition to orders-of-magnitude larger bandwidths, the small wavelengths at mm-wave enable high-dimensional multiple-input multiple-output (MIMO) operation. However, fully exploiting the advantages of mm-wave requires prohibitively high transceiver complexity when using conventional MIMO techniques. In this paper we propose and analyze the sum capacity of several linear, reduced-complexity multiuser MIMO (MU-MIMO) precoders that exploit the concept of beamspace MIMO (B-MIMO) communication - multiplexing data onto orthogonal spatial beams that serve as approximate channel eigenfunctions. Due to quasi-optical propagation at mm-wave, MIMO channels are expected to be low-rank and the low channel rank is manifested in the sparsity of the beamspace channel matrix. This enables near-optimal rank and complexity reduction via the concept of multi-beam selection. We present numerical capacity results that demonstrate the reduced-complexity B-MIMO precoders are able to closely approximate the performance of their full-dimensional counterparts with complexity that tracks the number of mobile stations (MSs). In mm-wave systems, where the number of MSs is expected to be much lower than the system dimension, this enables a considerable reduction in the digital signal processing complexity and in systems equipped with analog beamforming front-ends the hardware complexity is also reduced. Thus, the proposed reduced-complexity multiuser precoders provide a near-optimal route for achieving multi-Gigabit/s sum rates in mm-wave MU-MIMO networks with the lowest transceiver complexity.

Cognitive multiple access via cooperation: Protocol design and performance analysis

Abstract: In this paper, a novel cognitive multiple-access strategy in the presence of a cooperating relay is proposed. Exploiting an important phenomenon in wireless networks, source burstiness, the cognitive relay utilizes the periods of silence of the terminals to enable cooperation. Therefore, no extra channel resources are allocated for cooperation and the system encounters no bandwidth losses. Two protocols are developed to implement the proposed multiple-access strategy. The maximum stable throughput region and the delay performance of the proposed protocols are characterized. The results reveal that the proposed protocols provide significant performance gains over conventional relaying strategies such as selection and incremental relaying, specially at high spectral efficiency regimes. The rationale is that the lossless bandwidth property of the proposed protocols results in a graceful degradation in the maximum stable throughput with increasing the required rate of communication. On the other hand, conventional relaying strategies suffer from catastrophic performance degradation because of their inherent bandwidth inefficiency that results from allocating specific channel resources for cooperation at the relay. The analysis reveals that the throughput region of the proposed strategy is a subset of its maximum stable throughput region, which is different from random access, where both regions are conjectured to be identical.

Wireless information transfer with opportunistic energy harvesting

Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the flat-fading channel subject to the time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any given time due to the practical circuit limitation. As a result, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference conditions. In this paper, we derive the optimal mode switching rule at the receiver to achieve various tradeoffs between the minimum transmission outage probability for ID and the maximum average harvested energy for EH, which are characterized by the boundary of a so-called “outage-energy” region. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control and scheduling for information and energy transfer with the receiver's mode switching. Our results provide useful insights to the optimal design of emerging wireless communication systems powered by opportunistic WEH.

Effects of channel aging in massive MIMO systems

Abstract: Multiple-input multiple-output (MIMO) communication may provide high spectral efficiency through the deployment of a very large number of antenna elements at the base stations. The gains from massive MIMO communication come from the use of multiuser MIMO on the uplink and downlink, but with a large excess of antennas at the base station compared to the number of served users. Initial work on massive MIMO did not fully address several practical issues associated with its deployment. This paper considers the impact of channel aging on the performance of massive MIMO systems. The effects of channel variation are characterized as a function of different system parameters assuming a simple model for the channel time variations at the transmitter. Channel prediction is proposed to overcome channel aging effects. The analytical results on aging show how capacity is lost due to time variation in the channel. Numerical results in a multiceli network show that massive MIMO works even with some channel variation and that channel prediction could partially overcome channel aging effects.

Radio communication apparatus and radio communication method

Abstract: A radio communication apparatus that performs first radio communication using a first channel among two first channels each having a first channel width, and second radio communication using a second channel having a second channel width that is wider than the first channel width and also having a channel width overlapping with the two first channels. The apparatus includes an interference detection device which detects that interference occurs in the first channel among the two first channels, and a frame generation unit which generates a notification frame that recommends the use of only the first channel width. An instruction unit instructs the frame generation unit to generate the notification frame when the occurrence of interference is detected by the interference detection device. A frame transmission unit transmits the notification frame generated from the frame generation unit in response to the instruction from the instruction unit.