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In this paper, a Multiple-access channel is considered in which transmitters randomly located in the squared-shaped area of width D1. It is assumed the x and y coordinates of each transmitter's position are Uniform random variables and also the receiver is located at the origin. Hence, the distance between any transmitter-receiver pair and consequently, the path-loss term are random variables. It...
Various two-dimensional (2-D) OCDMA codes have been introduced in recent years due to their capabilities in enhancing cardinality, suppressing phase induced intensity noise (PIIN) and eliminates multiple access interference (MAI). This paper presents our new proposal of 2-D spectral/spatial Extended Enhanced Double Weight (2-D Extended-EDW) code. This code is designed to enhance cardinality and effective...
Across all cellular standards, manufacturers and service providers need to ensure the performance and compliance of their devices via manufacturing test. These tests are designed to demonstrate the ability of the cellular device to adhere to the requirements of a particular standard by exercising different functionality such as transmitter and receiver performance. With the continuing evolution of...
In WLAN systems, distributed coordination function (DCF) is used to avoid transmission collision. When an error occurs, the transmitter extends its contention window for the next retransmission to avoid more errors. But this may cause an unfairness problem; in noisy conditions MTs may find it difficult to get transmission opportunities, especially in a heterogeneous network with a large number of...
We address the transmission of discrete-time analog samples over a block fading Multiple Access Channel (MAC). At each transmitter, the source information is first encoded using analog Joint Source Channel Coding (JSCC) and then input to a MAC access scheme. We consider three different access schemes: Code Division Multiple Access (CDMA), linear MMSE access codes and opportunistic communication. CDMA...
The problem of coexistence among wireless networks, especially dissimilar ones competing for partially overlapping unlicensed bands, is becoming a hot topic. This is also confirmed by the mushrooming of mechanisms and working groups (within the International Bodies) addressing the issue. But prior to drawing any solution, an extensive theoretical analysis of the coexistence phenomena among any MAC...
Rendezvous problem is known as the fundamental issue in MAC design for cognitive radio networks (CRNs). With the concept of blind rendezvous, numerous channel-hopping sequence (CHS) based rendezvous schemes have been proposed to solve this problem. However, little attention is paid to the design of a CSMA/CA MAC based on these rendezvous schemes. In this paper, we propose a cooperative CSMA/CA MAC...
In this paper, we propose to use relay transmission as a powerful technique for performance improvement of free-space optical code-division multiple-access (FSO/CDMA) systems. Relay nodes are based on chip detect-and-forward to avoid decoding process that makes the relay nodes more complex. We formulate a closed-form expression for bit-error rate (BER) of proposed FSO/CDMA systems over log-normal...
In this paper we propose to implement direct-spread code-division multiple access (DS-CDMA) over powerline channels combined with blanking at the receiver to reduce the effect of impulsive noise (IN). Two spreading sequences are investigated in this study, namely, Walsh-Hadamard and polyphase codes. The impact of different loading scenarios, ranging from light-to full-loading, on the probability of...
Ranging by Time of Arrival (TOA) of Narrowband ultrasound (NBU) has been widely used by many locating systems for its characteristics of low cost and high accuracy. However, because it is hard to support code division multiple access in narrowband signal, to track multiple targets, existing NBU-based locating systems generally need to assign exclusive time slot to each target to avoid the signal conflicts...
Wireless sensor networks (WSNs) may lead to high traffic in network when nodes detect an event and become active to send the data to the sink. Therefore, traffic adaptive medium access control (MAC) protocol for WSNs, with a more strict collision avoidance technique, can help in resolving the issue of collision by allowing less number of sensor nodes to send the data on the shared wireless channel...
CSMA/CA protocol shows poor performance for multi-hop transmission due to intra-flow interference (IFI) caused by hidden terminal (HT) problem. We propose an IFI-cancelling (IFIC) multi-hop transmission scheme which can efficiently relay packets under high traffic load and fading environment by using a Known interference cancellation technique. It employs the least mean square (LMS) equalization process...
A major limiting factor in the performance of MIMO-CDMA systems is multiple access interference (MAI) which can reduce the system capacity as well as bit error rate (BER). Thus, statistical characterization of MAI is vital in analyzing the performance of such systems. Since, the statistical analysis of MAI in MIMO-CDMA is quite involved especially in the presence of fading channels, existing works...
In this paper, we address the multiuser detection problem in the presence of strong interference, mixture of Gaussian and α-stable noises. We initially obtain locally optimal (LO) detection rule for this problem which can almost completely suppress interference effect and combat α-stable noise to some extent using oversampling in the receiver or channel coding in the transmitter. Then, we derive a...
Full-duplex has emerged as a new communication paradigm and is anticipated to double wireless capacity. Existing studies of full-duplex mainly focused on its PHY layer design, which enables bidirectional transmission between a single pair of nodes. In this paper, we establish an analytical framework to quantify the network-level capacity gain of full-duplex over half-duplex. Our analysis reveals that...
In this paper we propose an optimized broadcasting mechanism which uses very limited signaling overhead. The main objective is to select the most appropriate relay nodes according to a given cost function. Basically, after receiving a broadcast packet each potential relay node computes a binary code according to a given cost function. Then, each node starts a sequence of transmit/listen intervals...
This paper presents the performance of a cooperative communication scheme when communicating over Rayleigh channel. More explicitly, the performances of the Code Division Multiple Access CDMA cooperative schemes with two and eight users, employing systematic convolutional code (CC) are presented. The single relay cooperative network with decode-and-forward (DAF) relay is investigated in the proposed...
An implementation of iterative joint detection for multiple access interference using direct-sequence code division multiple access is presented. Results for multiple field programmable gate array (FPGA) and multiple technology nodes for synthesized application specific integrated circuits (ASIC) are presented. The joint detection is based on iterative cancellation known as partition spreading (PS)...
In this paper, performance of a novel analytic model of direct sequence code division multiple accesses (DS-CDMA) using diversity with maximal ratio combining (MRC) scheme is observed under the influence of multipath Rayleigh fading and multi-access interference (MAI) varying different system parameters and properties of PN sequences. The analysis presents a mathematical expression for bit error rate...
Co-channel interference exists in IEEE 802.11 based wireless local area networks (WLANs) due to the limited number of non-overlapping channels in the current standards. In this paper, we investigate the impact of co-channel interference in carrier sense multiple access with collision avoidance (CSMA/CA) based WLANs via simulation. We find that the throughput unfairness among the users is severe in...
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