On the Stability of Contention Resolution Diversity Slotted ALOHA

In this paper a Time Division Multiple Access (TDMA) based Random Access (RA) channel with Successive Interference Cancellation (SIC) is considered for a finite user population and reliable retransmission mechanism on the basis of Contention Resolution Diversity Slotted ALOHA (CRDSA). A general mathematical model based on Markov Chains is derived which makes it possible to predict the stability regions of SIC-RA channels, the expected delays in equilibrium and the selection of parameters for a stable channel configuration. Furthermore the model enables the estimation of the average time before reaching instability. The presented model is verified against simulations and numerical results are provided for comparison of the stability of CRDSA versus the stability of traditional Slotted ALOHA (SA). The presented results show that CRDSA has not only a high gain over SA in terms of throughput but also in its stability.Comment: 10 pages, 12 figures This paper is submitted to the IEEE Transactions on Communications for possible publication. The IEEE copyright notice applie

Integrated voice/data protocols for satellite channels

Several integrated voice/data protocols for satellite channels are studied. The system consists of two types of traffic: voice calls which are blocked-calls-cleared and the data packets which may be stored when no channel is available. The voice calls are operated under a demand assignment protocol. Three different data protocols for data packets are introduced. Under Random Access Data (RAD), the Aloha random access scheme is used. Due to the nature of random access, the channel utilization is low. Under Demand Assignment Data (DAD), a demand assignment protocol is used to improve channel utilization. Since a satellite channel has long propagation delay, DAD may perform worse than RAD. The two protocols are combined to obtain a new protocol called Hybrid Data (HD). The proposed protocols are fully distributed and no central controller is required. Numerical results show that HD enjoys a lower delay than DAD and provides a much higher channel capacity than RAD. The effects of fixed and movable boundaries are compared in partitioning the total frequency band to voice and data users

Random Access in DVB-RCS2: Design and Dynamic Control for Congestion Avoidance

In the current DVB generation, satellite terminals are expected to be interactive and capable of transmission in the return channel with satisfying quality. Considering the bursty nature of their traffic and the long propagation delay, the use of a random access technique is a viable solution for such a Medium Access Control (MAC) scenario. In this paper, random access communication design in DVB-RCS2 is considered with particular regard to the recently introduced Contention Resolution Diversity Slotted Aloha (CRDSA) technique. This paper presents a model for design and tackles some issues on performance evaluation of the system by giving intuitive and effective tools. Moreover, dynamic control procedures that are able to avoid congestion at the gateway are introduced. Results show the advantages brought by CRDSA to DVB-RCS2 with regard to the previous state of the art.Comment: Accepted for publication: IEEE Transactions on Broadcasting; IEEE Transactions on Broadcasting, 201

Performance Enhancements for Asynchronous Random Access Protocols over Satellite

In this paper, a novel enhancement of the well known ALOHA random access mechanism is presented which largely extends the achievable throughput compared to traditional ALOHA and provides significantly lower packet loss rates. The novel mechanism, called Contention Resolution - ALOHA (CRA), is based on transmitting multiple replicas of a packet in an unslotted ALOHA system and applying interference cancellation techniques. In this paper the methodology for this new random access technique is presented, also w.r.t. existing Interference Cancellation (IC) techniques. Moreover numerical results for performance comparison with state of the art random access mechanisms, such as Contention Resolution Diversity Slotted ALOHA (CRDSA) are provided. Finally the benefit of taking strong forward error correcting codes for the performance of CRA is shown