Transmission Probability Control Research Articles

Distributed Transmission Probability Control in Fading Channel with State Information

A wireless system consisting of a finite number of heterogeneous users transmitting packets over a slotted ALOHA Rayleigh-fading channel is investigated in this paper. In this system, each user tries to minimize its number of transmission attempts while meeting the throughput demand. The user interaction in such an ALOHA network is modeled as a random access game. A novel technique to better exploit the channel state information (CSI) named adaptive CSI transmission method is proposed. Benchmarking with the no-CSI method and threshold-based CSI method, it is revealed that the proposed adaptive CSI method can yield up to 9.9% more throughput and 12.3% power reduction. Two simple yet effective guidelines on selecting among these CSI-related methods are formulated for systems with different SNRs and capture ratios. A distributed algorithm is proposed to find the optimal transmission probability. Both analytical and simulation results show that the algorithm exhibits fast convergence speed and is robustness against changes on the number of active nodes in the network.

Ad Hoc Self-Organizing (ASO) TDMA 방식 다중-홉 해양통신망에서의 실시간 전송 기법

본 논문은 VHF 대역을 사용하는 다중-홉 해양통신망에서 실시간 서비스를 제공하기 위해 제안된 DSTS(Dynamic Space-Time Subframe)기반 프레임 구조에서 다수의 MAC PDU로 구성된 데이터를 ASO-TDMA 전송 방식을 사용했을 때 발생되는 지연시간의 분포를 수학적으로 분석하고, 그 성능을 시뮬레이션을 통해 확인한다. 또한, 기존 전송방식에서 발생되는 지연시간을 단축시키는 동시에 시스템의 수율을 최대화하기 위한 연속적인 자원 할당 방식과 적응적 전송 확률 제어 방식을 제안하고, 기존 방식과 수율 성능을 비교한다. 이를 통해 본 논문에서 제안하는 방식은 DSTS 프레임 구조에서 다수의 MAC PDU에 대해서도 실시간 전송이 가능하고, 또한 수율 성능을 극대화할 수 있음을 보인다. In this paper, we first analyze the delay performance of Dynamic Space-time Subframe (DSTS)-based frame structure which has been proposed to support the real-time service as well as non real-time service, using Ad hoc Self-Organizing Time Division Multiple Access (ASO-TDMA) MAC protocol, especially when transmitting a MAC SDU with two or more MAC PDUs, in a multi-hop ad-hoc maritime communication network. We propose two key transmission schemes: contiguous DSTS reservation which guarantees the end-to-end delay for the multiple PDUs, and adaptive transmission probability control schemes to maximize the system throughput. Our simulation results show that the proposed schemes outperform the system throughput of the existing transmission schemes, while supporting the real-time requirement.

응답 라운드 조기종료와 전송확률 제어를 통한 STAC 프로토콜의 성능 개선

Auto-ID 센터에서는 13.56MHz RFID 시스템에서 다중 태그를 식별하기 위한 충돌 방지 알고리즘으로 STAC 프로토콜을 제안하였다. STAC 프로토콜에서는 다음 응답 라운드의 슬롯 개수를 결정하기 위하여 태그 수 추정 기법을 적용한다. 이 경우 추정한 태그의 수에 오차가 발생하면 충돌 또는 빈 슬롯이 많이 발생할 수 있으므로 식별 성능이 저하되는 문제점이 있다. 따라서 본 논문에서는 응답 라운드 동안 빈번한 충돌 또는 빈 슬롯이 발생하면 응답 라운드를 종료하는 기법과 태그의 전송확률을 제어하는 기법을 적용한 ERPB 알고리즘을 제안하고, 이에 대한 성능을 분석한다. 시뮬레이션을 통한 성능분석의 결과, 제안한 기법은 충돌률이 STAC 프로토콜에 비하여 39% 정도 낮으므로 태그 식별 시간이 짧음을 알 수 있었다. In 13.56MHz RFID system of Auto-ID center, STAC protocol is defined as an anti-collision algorithm for multiple tag reading. In STAC protocol, the reader uses the tag number estimation scheme to determine the number of slots for the next reply round. If errors occur in the estimated number of tags, the identification performances will be degraded due to a lot of collision or idle slots. Therefore, in this paper, we propose an ERPB algorithm that the reader cancels the reply round when it experiences a series of collision or idle slots during the current round. The transmission probability control for the tag is also applied to the proposed algorithm. Through simulations, it is demonstrated that the collision rate for the proposed scheme is about 39% lower than STAC protocol. Therefore, the proposed scheme can achieve faster tag identification time compared with STAC protocol due to the low collision rate.

Transmission Probability Control Scheme in FSA-based RFID Systems

This paper proposes a transmission probability control scheme for enhancing the performances of FSAbased RFID system. In order to maximize the system performance, the number of tags attempting to transmit their identifiers in a frame should be kept at a proper level. The reader calculates the transmission probability according to the number of tags within the identification range of reader and then broadcasts it to tags. Tags, in which their slot counter values reach to zero, attempt to transmit their identifiers with the received probability. Simulation results show that the proposed scheme can offer better throughput and delay performance than the conventional one regardless of the number of tags.

Opportunistic multi-channel CSMA protocol for OFDMA systems

In this letter, we present an opportunistic multichannel CSMA protocol for OFDMA systems in frequency-selective fading channel. In order to opportunistically exploit the frequency selectivity, an OFDM-based single-channel CSMA protocol can employ water-filling power allocation as it allows a single station to utilize the whole frequency bandwidth at each time instant. In contrast, the proposed OFDMA-based multichannel CSMA protocol achieves the multi-user diversity gain by arranging multiple stations to transmit on their favorable sub-channels simultaneously. The proposed protocol is designed as an opportunistic version of the original multi-channel CSMA protocol, which was proposed in our previous work, and adopts a channel-adaptive backoff (or transmission probability control) algorithm, enabling each station to attempt data transmission on its high-SNR sub-channel with a high probability. The opportunistic multi-channel CSMA turns out to improve the total data rate significantly over the opportunistic single-channel CSMA, and to achieve almost full multi-user diversity gain despite the distributed operation.

Centralized transmission probability control scheme for non-real-time traffic in wireless ATM networks

This article proposes a contention-based reservation medium access control protocol for transporting bursty traffic efficiently in wireless ATM networks. The proposed protocol is characterized by a contention-based transmission of the reservation request and a contention-free transmission of the bursty traffic. The design objective of the proposed protocol is to reduce the contention delay while maximizing the channel utilization. In order to reduce the collision of reservation request packets, the base station calculates and broadcasts the transmission permission probability of reservation request packets. The calculation of the transmission permission probability is based on the estimated load of reservation requests and the number of random access minislots. The wireless terminal, which has a bursty traffic, selects a random access minislot and transmits its reservation request packet with the received transmission permission probability. Based on the successfully received reservation packets, the scheduler allocates the uplink data slots to the wireless terminal. Simulation results are presented to show that the proposed protocol provides high channel utilization, and furthermore, maintains a constant delay performance in a heavy traffic environment.

Centralised transmission probability control scheme for fair packet data services in CDMA S-ALOHA system

A transmission probability control scheme for guaranteeing fair packet transmissions in the CDMA S-ALOHA system is proposed. The base station calculates the transmission probability according to the offered loads and then broadcasts to all the mobile stations, and mobile stations attempt to transmit the packet with the received probability. Simulation results show that the proposed scheme can offer better performance than the conventional one, and guarantee a good fairness among all the mobile stations regardless of the offered loads.

Maximization of the channel utilization in wireless heterogeneous multiaccess networks

The key aspect of personal communication services (PCS) is wireless access through local and wide area networks where there may exist a variety of services having different rates and diverse quality-of-service (QOS) requirements. This paper addresses the problem of maximizing the channel utilization in a wireless heterogeneous network with finite population. Slotted ALOHA with packet capture is used as the multiaccess protocol in the presence of background noise and Rayleigh fading. It is known that the capture effect, while significantly increasing the network throughput, causes unfairness among users in a heterogeneous network. To take fairness into consideration, individual throughput is used as the constraint with the channel utilization being the maximization objective. The maximization problem is then studied under various conditions by controlling the transmission power and/or probability. It is shown that for a narrow-band system under equal individual throughput requirement, transmission probability control is more effective than power control, and when a joint control strategy is employed, perfect or near perfect channel utilization can be achieved in the absence or presence of Rayleigh fading.