Capture Division Packet Access Research Articles

Plane cover multiple access: a new approach to maximizing cellular system capacity

We develop a new media access control strategy, called plane cover multiple access (PCMA), that provides a means of allocating wireless bandwidth in a packet-based cellular system. PCMA seeks to maximize the number of parallel transmissions among cells by defining virtual cells in which users transmit using a given reuse factor. By keeping the reuse factors low, system throughput can be maximized. We show that the throughput of a simple system designed using PCMA is up to 82% more efficient than capture division packet access (CDPA), the best known alternative for the cellular mobile environment.

A unified framework for the study of wireless packet access in the presence of slow propagation impairments

The paper introduces a unified analytical framework which allows accurate study of multiple access performance in wireless packet systems. The method is based on the analysis of the interference statistics and takes into account slowly varying shadowing and best base station assignment, as well as the effect of the nonuniform traffic distribution induced transmission failures. As an example of application of the technique, two protocols are considered: (1) the classic slotted ALOHA, for which a comprehensive study in a realistic wireless environment has not yet been presented, despite the many analyses published in the past; and (2) the capture division packet access (CDPA). An important conclusion of our study is that if power control and best cell site assignment are jointly used, the performance loss due to slow shadowing is almost negligible.

Retransmissions versus FEC plus interleaving for real-time applications: a comparison between CDPA and MC-TDMA cellular systems

The capacity of mobile cellular systems is mainly limited by cochannel interference. Commonly in multiple carrier-time division multiple access (MC-TDMA) systems, like the global system for mobile (GSM) communications, the interference noise is first reduced by means of channel clustering and slow frequency hopping. The residual interference, characterized by a level varying slot by slot, causes errors in burst which are spread with bit interleaving and fought with correcting codes for random errors. With real-time services like voice, no other error control technique, such as automatic repeat request (ARQ), is usually adopted. An alternative approach is given by capture division packet access (CDPA) where transmissions are spread in time adopting a dynamic slot assignment (DSA), and errors are dealt with a retransmission mechanism. In this paper, we present a comparison of this two approaches, and using a simple theoretic capacity analysis, we justify the better performance of CDPA. Moreover, by the delay performance analysis, we prove that in spite of its retransmission mechanism, CDPA is effective also with delay constrained services.

Slow shadowing and macrodiversity in the capture-division packet access (CDPA)

Recently, a new method for achieving spectrum reuse in cellular systems, called Capture-Division Packet Access (CDPA), has been introduced. The method uses a single frequency in all cells, and expl...

Slotted ALOHA and CDPA: a comparison of channel access performance in cellular systems

The paper compares the performance of two channel-access schemes suitable for the cellular environment, which, in particular, allow the packet capture and can deal with inter-cell interference. The first scheme is the well known S-ALOHA while the second one is the Capture Division Packet Access, recently proposed. The comparison is analytically performed over a common system with a common analytical model. Despite the many analyses appeared on S-ALOHA, the one we develop is new because a throughput density uniformly distributed on the plane is considered in a multiple cell environment. The analysis clearly shows the effect of intra-cell and inter-cell interference on the ALOHA system and quantifies the throughput gain achieved by CDPA, which completely avoids intra-cell interference. Our analysis also provides insight about the effectiveness of power control on both systems.

Performance of capture-division packet access with slow shadowing and power control

A new method for achieving improved spectrum reuse in cellular systems, called capture-division packet access (CDPA), has been introduced. The method uses a single frequency in all cells, but, unlike code-division multiple access (CDMA), it allows each transmitter to exploit the full bandwidth. Practically, the CDPA's way of operation can be seen as a slotted ALOHA scheme among different cells in which the mobile terminals belonging to the same cell transmit using a collision-free mechanism, which is easily obtained due to the very short intracell propagation delay. Parallel transmission in different cells is achieved through the "capture" capability. Packets that are not captured are almost immediately retransmitted, thus assuring that packets are eventually correctly received. We analyze the performance of the CDPA in the presence of slowly varying shadowing. The gain offered by power control techniques is also investigated. Finally, the effect of erroneous signaling information is studied, and a delay analysis is presented.

Capture-division packet access for wireless personal communications

This paper presents a new architecture for the third-generation mobile systems, capture-division packetized access (CDPA), that overcomes most of the limitations of present cellular systems. It addresses the three main issues of radio access, namely the channel reuse, the multiple access, and the handover problems, in complete adherence to packet-switching principles. The CDPA channel reuse mechanism is a completely new alternative with respect to time-division, frequency-division, or code-division multiple-access (TDMA, FDMA, and CDMA, respectively), which achieve communication parallelism by subdividing the bandwidth a priori among cells. In CDPA, a single frequency channel is used and parallel transmissions are achieved through the capture capability of receivers. The hybrid reservation-polling multiple access mechanism used in CDPA is able to integrate any kind of traffic and guarantees almost immediate retransmission of packets that are not captured, thus assuring their correct reception. Finally, the packet-switching approach allows connectionless communications with any base station (BS), and eliminates the need for extra radio traffic in managing handovers. This turns out to be very effective in local area systems where the required high bandwidth is obtained by using a pico-cell structure. We present the CDPA architecture, discuss some implementation issues, and evaluate its performance under a variety of system parameters and operating conditions, using analytical and simulation methods.

Capture division packet access: a new cellular access architecture for future PCNs

The authors describe a new cellular access architecture, known as capture-division packet access, which is a packet-oriented architecture able to support the constant bit rate traffic and variable bandwidth on demand necessary for multimedia traffic. The approach integrates the multiple access and channel reuse issues to achieve a high degree of spectral efficiency, and presents general advantages even if used for delay-constrained circuit-oriented traffic. Unlike CDMA and TDMA, wherein the effective data rate of each connection is typically a small fraction of the total radio channel allocated for PCN, the CDPA approach allows each user to access the entire channel, if necessary, for brief periods of time (packet access). Spectrum sharing is accomplished by exploiting the different path losses suffered by the various signals as they appear at the base stations (the capture effect), with co-channel interference abated through time diversity (colliding users do not successively retry in the same time interval). Results suggest that abating co-channel interference by random retransmission may be more effective than spatial isolation at cells using the same channel, as is usual in FDMA-TDMA systems.