Channel Load Sensing Protocol Research Articles

Performance Analysis of CDMA/ALOHA Networks in Memory Impulse Channels

Previous CDMA/ALOHA network performance analysis papers do not consider memory impulse channels. The Markov-Gaussian model can characterize the bursty nature of the memory impulsive noise in some wireless channels and power line communication (PLC) channels. In this paper, we propose the use of the Markov-Gaussian model in the throughput analysis of CDMA/ALOHA networks. The state transition diagram for the throughput analysis has one extra dimension to represent if the impulse noise is present or not. We derive the exact throughput analysis in memory impulse channels with and without channel load sensing protocol (CLSP). The analytic results demonstrate that if the level of the impulsive noise is higher, performance degradation is more and vice versa. Based on the analytic results, we also find the optimal CLSP threshold alpha for various impulse noise conditions. The analytic results of the throughput performance are all matched by the simulation results.

Throughput Performance Analysis of Asynchronous Optical CDMA Networks With Channel Load Sensing Protocol

In this paper, we propose a channel load sensing protocol (CLSP) to prevent the throughput decrease at heavy traffic conditions in asynchronous optical code-division multiple-access (CDMA) networks. The multiple access-interference (MAI) and beat noise are considered the main deleterious source of the network in addition to thermal, shot, and relative intensity noises. Moreover, we employ optical hard limiters and error correction codes to mitigate the physical channel impairments. However, the packet throughput performance declines severely when the number of active users reaches a certain amount in the network. We employ the proposed CLSP with optimum threshold that successfully mitigates the throughput reduction at heavy load conditions. Numerical results show that the proposed protocol can support a throughput rate above 100 Gb/s, which might be compatible for an eventual standardization for broadband optical access networks.

A Reasonable Throughput Analysis of the CSK/SSMA Unslotted ALOHA System with Nonorthogonal Sequences

In this paper, the throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences which combines the ALOHA system with Code Shift Keying using nonorthogonal sequences is analyzed. In this system, the nonorthogonal sequences are constructed by concatenating Mcon orthogonal sequences. The throughput performance of the CSK/SSMA ALOHA system with nonorthogonal sequences is analyzed in consideration that the number of packets changes at intervals of one orthogonal sequence. Moreover, the throughput performance of our system with Channel Load Sensing Protocol (CLSP) is also analyzed. We also examine the influence of unreachable control signal of CLSP. Consequently, it is found that the throughput performance of our system decreases significantly by this analysis. It is also found that the throughput performance of our system improves greatly by using CLSP. However, the unreachable control signal affects the throughput performance of this system, seriously.

Packet-length adaptive CLSP/DS-CDMA: performance in burst-error correlated fading channels

The authors analyze throughput-delay performance of an unslotted channel load sensing protocol (CLSP)/direct sequence (DS)-code division multiple access (CDMA) packet radio network (PRN) with adaptive packet length over burst-error correlated fading channels. CLSP controls the packet access in uplink of unslotted ALOHA/DS-CDMA systems so that contention is avoided and throughput is maximized. However, due to high uncertainty of radio channels, the performance of CLSP/DS-CDMA PRN may suffer from notable degradations. Using theoretical analysis and simulation, the authors show that in highly correlated fading environments adapting the length of radio packets to fading conditions significantly improves system performance and energy efficiency of mobile terminals. In their modeling, they study the relation between the fade statistics and the packet length in correlated Rayleigh fading channels. The effects of reception diversity, imperfect transmit power control (TPC), and user mobility are considered. The results are used to develop simple, energy-efficient, and robust adaptation mechanisms.

Performance analysis of DS/SSMA unslotted ALOHA system with variable length data traffic

We analyze the throughput of a direct-sequence spread spectrum multiple access (DS/SSMA) unslotted ALOHA system with variable length data traffic. The system is analyzed for two cases: (1) systems without a channel load sensing protocol (CLSP) and (2) systems with a CLSP. The bit-error probability and the throughput are obtained as a function of the signal-to-noise ratio (SNR) during message transmission, considering the number of overlapped messages and the amount of time overlap. We assume that the generation of data messages is Poisson distributed and that the messages are divided into packets before transmission. The system is modeled as a Markov chain under the assumption that the number of packets in a message is geometrically distributed with a constant packet length. The throughput variance of the DS/SSMA unslotted ALOHA system with variable length data traffic is obtained as the Reed-Solomon code rate varies. Results show that a significant throughput improvement can be obtained by using an error-correcting code.

Throughput analysis of DS/SSMA unslotted ALOHA system with fixed packet length

Throughput analysis of direct-sequence spread spectrum multiple access (DS/SSMA) unslotted ALOHA with fixed packet length is presented. As the levels of multi-user interference fluctuate during the packet transmission, we calculate the packet error probability and the throughput by considering not only the number of overlapped packets but also the amount of time overlap. On the assumption that packet generation is Poisson, the system can be thought as the queueing system M/D//spl infin/. With Gaussian approximation of multi-user interference, we obtain the throughput as the function of the number of chips in a bit, the packet length, and the offered load of the system. We also analyze the channel load sensing protocol (CLSP), and obtain the optimum threshold of CLSP.

A novel spread slotted Aloha system with channel load sensing protocol

This paper presents a novel spread slotted Aloha system with channel load sensing protocol (CLSP). CLSP is an effective scheme to improve the throughput performance in spread unslotted Aloha systems. In spread slotted Aloha systems, however, it does not make sense to utilize CLSP because the slot size is usually the same as the packet size. The slot size of the proposed system is set less than the packet size, thereby enabling the authors to apply CLSP and improving the throughput performance. Another feature of the proposed system is that the system is not likely affected by the time difference between channel load sensing and timing of packet access, which they call the access timing delay. Throughput performance of the proposed system is evaluated in the presence of the access timing delay and a significant increase of the throughput is shown compared with that of spread unslotted Aloha with CLSP.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>