Satellite Network Oriented TCP Slow Start Algorithm

Currently there is no control for real-time traffic sources in IP networks. This is a serious problem because real-time traffic can not only congest the network but can also cause unfairness and starvation of TCP traffic. A new rate control scheme, RCS, is introduced for real-time traffic in networks with high bandwidth-delay products and high bit error rates. RCS is based on the concept of using dummy packets to probe the availability of network resources. Dummy packets are treated as low priority packets and consequently they do not affect the throughput of actual data traffic. Therefore, RCS requires all the routers in the connection path to support some priority policy. Simulation experiments show that in environments with high bandwidth-delay products and high bit error rates, RCS achieves good throughput performance without penalizing TCP connections.

위성 통신은 넓은 지역에 통신 서비스를 제공하는 광역 네트워크이다. 하지만, 위성 통신은 대역폭이 제한되고 매우 긴 전파 지연 시간과 높은 BER(Bit Error Rate)로 인해 위성 통신을 고려하지 않은 TCP의 성능이 저하 된다. 본 논문에서는 위성 통신에서의 TCP 성능을 향상시키기 위해 DVB-RCS(Digital Video Broadcasting-Return Channel via Satellite) 네트워크 환경을 고려한 cross-layer 기반 PEP(Performance Enhancing Proxy) 기술을 제안한다. 제안하는 프로토콜은 TCP와 링크 계층 간 위성 자원 할당 정보를 정보 교환을 통해 최적의 TCP CWND(Congestion Window)를 설정한다. 제안한 프로토콜의 성능 평가를 위해 리눅스 기반의 PEP 테스트 베드를 구현하였다. 성능 평가 결과 다양한 BER에서 제안한 프로토콜은 위성 자원 할당 정보를 이용하여 최적의 TCP CWND 크기를 설정하기 때문에 단일 및 다중 세션 환경에서 기존 TCP 보다 제안한 프로토콜이 더 좋은 성능을 보여준다는 것을 확인할 수 있었다. Satellite communication is a wide area network (WAN) which provides communication service worldwide. However, the performance of TCP can be seriously degraded in the satellite networks due to limited bandwidth, long round-trip time (RTT) and high bit error rate (BER) over satellite links. In order to improve the performance of TCP, this paper proposes cross-layer Performance Enhancing Proxy (PEP) in digital video broadcasting-return channel via satellite (DVB-RCS) networks. The proposed protocol sets TCP Congestion Window (CWND) size by using satellite resource allocation information exchanged between TCP and the link-layer. we implement PEP testbed based on Linux to evaluate the performance of the proposed protocol. The simulation results show that the proposed protocol performs better than standard TCP both in single and multiple sessions in variant BER, because the proposed protocol sets TCP CWND size by using satellite resource allocation.

Modified Packet Combining (MPC) scheme is an error correction scheme, which can correct double or, higher bit errors. In some earlier work, a scheme known as Packet Reversed Packet Combining (PRPC) scheme that will correct error if occurs at same bit location of erroneous copies, was studied. Both PRPC and MPC scheme are believed to offer higher throughput and better error correction capability at high bit error rate (BER) and large packet size only. Exact analysis was performed to substantiate this claim of higher throughput and better error correction capability in high as well as in low bit error rate (BER) for large and medium packet size. To combat high bit error rate some researches proposed to use Error Correction Code (ECC) in place of Error Detection Code (EDC) in ARQ scheme. But no conclusive result is found to justify the idea in terms of throughput. The current investigation is an attempt to explore the basic gap. In this paper, we investigate the exact analysis of both PRPC and MPC in a Modified way over Conventional PRPC, and report the findings thereof. We propose a combined protocol of Modified PRPC and MPC, and find that it will offer higher throughput and better error correction capability at high and low BER with medium and large packet size as we have used MPC (Modified Packet Combining) scheme with PRPC (Packet Reverse Packet Combining) scheme in a Modified way by combining BEC (Backward Error Correction) with FEC (Forward Error Correction) Codes for Mobile Communication and Networks.

As the Internet dramatically changes the world, applications that based on TCP/IP are taking up an increasing proportion in satellite services. Since there are characteristics such as long round trip delay and high bit error rate in satellite communication links, when combined with TCP/IP services, it will lead to frequently data resending and decrease network throughput. An accelerator based on Space Communication Protocol Standard Transport Protocol (SCPS-TP) has been designed and presented in this paper functioning as a Performance Enhancing Proxy (PEP) to improve TCP performance in satellite IP networks. Testing results show that satellite IP networks using the accelerator can achieve higher throughput performance, shorter transfer delay, better stability and stronger flexibility. The accelerator is totally transparent to the applications, and therefore it could be applied to any kind of space communication, and it could also meet the demand for rapid response in military, earthquakes and other emergencies.

Internet has developed into dynamic network where users use wired/wireless access technologies. The diversity of bandwidths, delays and error rates observed on Internet have increased. TCP is the common denominator for many services therefore by modifying TCP the need for applying solutions locally can be reduced. We focus on making TCP more efficient in a way to speed up its slow start phase. Different Slow Start algorithms will be analyzed and new variant will be proposed.

Nomadic computing imposes a set of serious problems and new requirements onto middleware platforms supporting distributed applications. Among these are the characteristics of wireless links like sudden and frequent disconnection, long roundtrip times, high bit error rates and small bandwidth. But there are also new requirements like handover support and the necessity to use different networks (bearers). All these problems and requirements lead to the demand for an association between client and server that is independent of a transport connection. In this paper, we present a session layer that provides such an association for the middleware platform CORBA based on the Wireless Application Protocol (WAP) that is especially designed for mobile and wireless devices. It turns out that the session protocol in WAP called WSP is not able to fulfill our requirements, thus, it was necessary to define our own session layer. The session layer provides explicit and implicit mechanisms to suspend and resume a session, a reconnection to the session after the bearer was lost or changed and a solution to the lost reply problem. Furthermore, it contains an interface to be used by session-aware applications to control the presented mechanisms themselves on a fine-grained level. This paper presents a detailed description of the session layer, its integration into CORBA, a mapping of GIOP messages onto WTP and selected implementation details

In terrestrial-satellite hybrid networks, traditional TCP performance degrades a lot due to long propagation delays and high bit error rates link. Performance enhancing proxy(PEP) can shorten round trip time loop time and Peach can enhance the performance over high bit error rates link. In this paper, we propose a new scheme that combines PEP and TCP Peach for terrestrial-satellite hybrid networks. The scheme could reduce the negative impact on performance (in terms of throughput). To obtain an analysis result, we also introduce a mathematic model for our PEP. The analysis and simulation results demonstrate that our scheme could significantly improve the network performance than traditional TCP protocols.

Different from terrestrial sensor networks, underwater sensor networks use acoustic channels for communication and most sensor nodes are mobile due to water current. These distinctions feature underwater sensor networks with highly dynamic topology, high bit error rate, large propagation delay, and low available bandwidth. Traditional ARQ series are not suitable due to their frequent feedbacks, which is undesirable in underwater environment. On the other hand, pure FEC can't apply into underwater sensor networks, not only because of its complexity, but also because it needs some feedbacks. This paper studied transport protocol in underwater sensor networks, implemented a reliable lightweight RFEC-based encoding and decoding algorithm. Then combine the algorithm with ARQ to a transport protocol. In this way, take advantages of FEC to deal with high bit error, and ARQ to avoid feedbacks. Through simulation experiment on method of random sequences generation, parameters selection, and transmission strategy, some useful conclusion is gotten. It provides practical data and references on practical application of underwater sensor networks.

Near-threshold voltage (NTV) operation is expected to enable up to 10× energy-efficiency for future processors. However, reliable operation below a minimum voltage (Vccmin) cannot be guaranteed. Specifically, SRAM bit-cell error rates are expected to rise steeply since their margins can easily be violated at near-threshold voltages. Multicore processors rely on fast private L1 caches to exploit data locality and achieve high performance. In the presence of high bit-cell error rates, an L1 cache can either sacrifice capacity or incur additional latency to correct the errors. We observe that L1 cache sensitivity to hit latency offers a design tradeoff between capacity and latency. When error rate is high at extreme Vccmin, it is worthwhile incurring additional latency to recover and utilize the additional L1 cache capacity. However, at low error rates, the additional constant latency to recover cache capacity degrades performance. With this tradeoff in mind, we propose a novel private L1 cache architecture that dynamically learns and adapts by either recovering cache capacity at the cost of additional latency overhead, or operate at lower capacity while utilizing the benefits of optimal hit latency. Using simulations of a 64-core multicore, we demonstrate that our adaptive L1 cache architecture performs better than both individual schemes at low and high error rates (i.e., various NTV conditions).

Satellite communication has become important in the current global data communication due to its large coverage area. Satellite links are affected by two major concerns: long propagation delays, and relatively high error rates. Standard TCP congestion control variants were not designed to address these challenges. They generally depend on round trip times (RTTs), and hence suffer heavily if the RTTs are large. Various TCP variants like Hybla have been proposed in order to optimize the channel throughput in heterogeneous networks incorporating satellite links. The error rate of satellite channels can be substantially mitigated using forward error correction (FEC) techniques. In such a situation, according to the results obtained by our comparative study, the performance of Cubic, which is designed for high-speed networks, is better than Hybla, in conditions of high-latency and low error rates.

SUMMARY With the rapid development of wireless network technologies, heterogeneous networks with wired and wireless links are becoming common. However, the performance of TCP data transmission deteriorates significantly when a TCP connection traverses such networks, mainly because of packet losses caused by the high bit error rate of wireless links. Many solutions for this problem have been proposed in the past literature. However, most of them have various drawbacks, such as difficulties in their deployment by the wireless access network provider and end users, violation of TCP’s end-to-end principle by splitting the TCP connection, or inapplicability to IP-level encrypted traffic because the base station needs to access the TCP header. In this paper, we propose a new mechanism without such drawbacks to improve the performance of TCP over wired and wireless heterogeneous networks. Our mechanism employs a receiver-based approach, which does not need modifications to be made to the sender TCP or the base station. It uses the ACK-splitting method for increasing the congestion window size quickly in order to restrain the throughput degradation caused by packet losses due to the high bit error rate of wireless links. We evaluate the performance of our mechanism and show that our mechanism can increase throughput by up to 94% in a UMTS network. The simulation results also show that our mechanism does not significantly deteriorate

In this paper, Multiple Input Multiple Output (MIMO) system with Space-Time Block Code (STBC) technique is used to satisfy the recent demands in the wireless communication system. That means the system should support the system’s high data rate, reliability, and performance in terms of the bit error rates. For achieving high data rates and high reliability, the antennas at the transmitter and the receiver side of the communication system should increase. Here we consider the 8 × 8 system it consists of eight antennas at both transmitter and receiver side. This 8 × 8 system matrix will design based on almouti codes. This almouti code with the STBC technique gives full data rates and high reliability. So by increasing the antennas, the high data rates by splitting the among the transmitter antennas. In this system at the receiver, the linear processing of the maximum likelihood (ML) decoding technique simplifies the decoding complexity. The simulation result shows the achieving high bit error rate (BER) and the channel capacity. The (8, 8) system outperforms the previous system without increasing the receiver decoding complexity.KeywordsMIMOSTBCML decoding

In order to solve the problems of the traditional anti-jamming algorithm of broadband wireless communication, such as poor anti-jamming performance and high bit error rate, an anti-jamming algorithm of broadband wireless communication based on Embedded MCU is proposed. In the broadband wireless communication based on embedded single-chip microcomputer, the m-sequence of communication signal data is constructed, encoded and decoded. Finally, CRC redundancy test and error correction are carried out for the decoded communication data, so far the design of broadband wireless communication anti-interference algorithm based on embedded single-chip microcomputer is completed. Through the contrast experiment, compared with the traditional anti-jamming algorithm of broadband wireless communication, the experimental results show that compared with the traditional anti-jamming algorithm of broadband wireless communication, the proposed anti-jamming algorithm of broadband wireless communication based on Embedded MCU has lower bit error rate, which shows that it has better anti-jamming ability.

While Transmission Control Protocol (TCP) works well with a low bit error rate (BER), the performance of TCP degrades significantly if the BER rises above a certain level. A study of the performance of TCP with high BER is required for the efficient design and deployment of such systems. In this paper, we address the problem of TCP performance in high BERs and analyze the issues by investigating the effect of BERs on system performance. We consider TCP Reno in our study to explore the system performance using extensive analysis of simulation and modeling. In the analysis, we consider the amount of datagram sent and retransmitted, mean throughput, link-layer overhead, TCP window size, FTP download response time, packet dropping and retransmission, and the TCP congestion avoidance mechanism. We validate simulation results by setting up a virtualized testbed using Linux hosts and a Linux router. The results obtained show that TCP throughput degrades significantly and eventually collapses at the packet drop probability of 10% (BER = 10−5). The FTP download response time is about 32 times longer than that of a perfect channel (no packet dropping). We found that TCP Reno cannot handle such a high BER to operate in wireless environments effectively. Finally, we provide recommendations for network researchers and engineers confronted with the challenge of operating TCP over noisy channels.

In order to solve the high bit error rate (BER) caused by rate oscillation in traditional Data Rate Change (DRC) algorithm, an improved DRC algorithm based on Adaptive Frame Length (AFL) was proposed. Firstly, the frame length and transmission rate of the initial transmission were determined by the parameters of the current channel and the information of previous empirical values. Then, if two frames with the same length were successively sent in the transmission process, the frame length would be accordingly increased. If the retransmission failed twice in a row, the frame length would be halved in the next transmission. Finally, the frame error rate was calculated based on the current frame length. The data rate would be updated If the value was less than the present threshold. Compared with RapidM DRC, the average bit error rate of the link decreased by 4.8 percentage points, and the link availability increased by 10 percentage points. The experimental results show that the proposed algorithm can eliminate the rate oscillation and improve the communication capability of the HF communication system.