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Wireless communication in the 60GHz millimeter wave (mm-wave) communications is getting increasing attention as a promising candidate for gigabits per second (Gbps) wireless communication networks. Although multi-Gbps throughput is supported and a very large block of unlicensed spectrum is available worldwide in the 60GHz band, some technical challenges exist towards making 60GHz wireless network...
This paper presents a protocol designed as an alternative to classical TCP for channels which experience high loss-rates. The protocol is simplified with respect to TCP by eliminating the need of retransmissions and the associated buffers. This is achieved by applying a rateless erasure correcting code to the data that is going to be transferred. A modified version of the TCP congestion control algorithms...
In this paper, we first investigate the relationship between packet length and packet loss rate in the Gilbert wireless error model. Then we propose a congestion control scheme which can detect the nature of packet losses by sending large and small packets alternately. By means of updating factor and loss queue, this proposed scheme can adapt to the changes of network states quickly and improve delivery...
In this paper, a centralized polling-based medium access (MAC) scheme, namely, the IEEE 802.11e hybrid coordinator function (HCF) controlled channel access (HCCA), is considered as an alternative to the current MAC protocol used in IEEE 802.11p for Wireless Access in Vehicular Environment (WAVE). At first, the limitations of the current enhanced distributed channel access (EDCA) are examined, and...
TCP has been a congestion control method in the Internet. However, since TCP is not able to directly measure the network status from the end nodes, the TCP window control gradually increases the congestion window size until congestion occurs. This control gets network bandwidth aggressively and affects communication of all stations (STAs) which belong to the same access point of IEEE 802.11 standards...
The capacity problem is one of the main issues in researching the multi-channel IEEE 802.11 wireless networks. In this paper, we analyze the path capacity of the multi-channel wireless networks by estimating the RTS, CTS and the packet loss rate of the wireless links and calculating the average service time of the packet sending. We also analyze the channel assignment and channel switching problems...
In this paper, we explore the feasibility of achieving gigabit baseband throughput using the vast computational power offered by the graphics processors (GPUs). One of the most computationally intensive functions commonly used in baseband communications, the Fast Fourier Transform (FFT) algorithm, is implemented on an NVIDIA GPU using their general-purpose computing platform called the Compute Unified...
In recent years ICT technology is gaining importance to the railway environment, more specific in the networking on-board of trains. One of the first drivers was the “always connected” idea for mobile users, but in the mean time this idea has evolved beyond providing pure Internet access for passengers, to a better way of managing the trains in all aspects. This includes comfort services like passenger...
Spatial processing techniques are considered as means to enhance the performance of WLANs systems. Different multi-antenna methods exploit different properties of the radio channel, so in this paper, we identify, based on the channel state, the physical layer parameters that can be controlled in the attempt to satisfy the user/application requirements, with an efficient use of the available radio...
Channel-aware scheduling in modern wireless networks enables the system to exploit the random rate variations across different users to increase the performance of the system. We analyze channel-aware priority-based downlink scheduling policies at the so-called flow level with a stochastically varying number of users. The priority can be any monotonously increasing function of the instantaneous rate...
The 802.11 standards specify several transmission rates that can be used at the MAC layer protocol to adapt the transmission rate to channel conditions. Such dynamic adaptations can improve per-hop performance in Wireless Networks and therefore can have impact on the Quality of Service provided for communicating applications. In this paper we present a comprehensive evaluation of the performance of...
Optimal capacity analysis in multi-radio multi-channel wireless networks by nature incurs the formulation of a mixed integer programming, which is NP-hard in general. The current state of the art mainly resorts to heuristic algorithms to obtain an approximate solution. In this paper, we propose a novel concept of multi-dimensional conflict graph (MDCG). Based on MDCG, the capacity optimization issue...
Current Internet protocols like TCP have been designed to work well on channels with low channel error rates. Wireless channels on the other hand exhibit high loss rates when compared to wired channels. Current TCP implementations usually attribute packet losses caused by channel errors as being actually caused by congestion. The result is an unnecessary reduction of the sending rate which leads to...
IEEE 802.22, also called Wireless Regional Area Network (WRAN), is the newest wireless standard being developed for remote and rural areas. In this paper an overview of the standard, and more specifically its PHY layer is introduced. In order to evaluate the performance of the system, we model the PHY layer in MATLAB/SIMULINK and extract the Bit Error Rate (BER) of the system for different code rates...
Transmit beamforming increases throughput and transmission range of a wireless communication system. However, the required feedback of channel state information (CSI) consumes radio resources that otherwise can be used for data transmission. This makes "Feedback or no feedback?" a relevant question to ask. This paper answers this question by proposing intelligent feedback control using a...
This paper focuses on the unslotted cognitive radio networks in which the secondary users (SUs) are not synchronized with the primary users (PUs). The SUs can opportunistically utilize the wireless channel as long as the channel is not occupied by the PUs. Due to the half-duplex nature of the wireless medium, the SUs may inevitably impose interference to the PUs because the SUs cannot precisely predict...
The problem of cognitive access of channels of primary users by a secondary user is considered. The transmissions of primary users are modeled as independent continuous-time Markovian on-off processes. A secondary cognitive user employs slotted transmissions, and it senses one of the possible channels before transmission. The objective of the cognitive user is to maximize its throughput subject to...
Abstract-In this paper, we propose a dynamic OFDMA based subcarrier/power allocation scheme, which aims to balance the aggregate rate and the achieved TCP throughput of competing TCP flows. The proposed allocation utilizes the theoretical TCP throughput which can be accomplished in the end-to-end path. In doing so, the TCP aware scheme attempts to minimize the gap between the allocated rate and the...
Hybrid Automatic-Repeat-reQuest (ARQ) schemes are capable of maintaining reliable communications for transmission over hostile wireless channels. In coherent detection aided schemes, the achievable performance substantially depends on the accuracy of channel state information (CSI). In this paper, the impact of imperfect CSI on Reed-Solomon (RS) coded HybridARQ systems is investigated for transmission...
In this paper, we study opportunistic multicast scheduling (OMS) in a wireless network with a central base station (BS) broadcasting a common packet to multiple users with different instantaneous channel conditions. Our objective is to minimize the broadcast latency, which is defined as the total transmission time required for all intended users in a multicast group to receive the packet. Based on...
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