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Wireless networks poses a major challenge for TCP, as packet loses due to channel interference and fading rather than network congestion. By utilizing a cross-layer mechanism to distinguish cause of packet loss, the mobile-host-centric transport protocol (MCP) can achieve higher performance than TCP Reno in WLAN. In this paper, we proposed a new cross-layer feedback mechanism and congestion control...
We analyzed the requirement of MAC protocol in coal mine, and proposed an improved 802.11 protocol which can adopt RTS/CTS mechanism or not adaptively. This protocol switch the status of RTS/CTS mechanism by comparing the optimal switch value of collision probability with real-time collision probability. The computing formula of switch threshold was given. Simulations show that the adaptive RTS adjustment...
For Reed-Solomon (RS) codes, due to the message dependency, there exists a performance gap between the adaptive belief propagation (ABP) and the maximum likelihood decoding (MLD) algorithms. Aiming at reducing the gap at the cost of some complexity, based on the fact that ABP has the characteristic of soft-in-soft-out (SISO) and errors often happen in the positions with lower reliability values for...
In this paper, we address retransmission strategies of the generation-based network coding in the packet network. Our discussion focuses on how to make the retransmission more efficient. We investigate four retransmission strategies, quasi Classical ReTransmission strategy (CRT), Random ReTransmission strategy (RRT), Packet-Loss-Edge-based ReTransmission strategy (PLERT) and Minimum ReTransmission...
Random network coding based on the generation concept provides various benefits such as reduced system complexity. However, various generation updating processes used in general result in a throughput loss. In this paper, we propose a network coding scheme using a concept we call ??generation crossing??. We also introduce a full cardinality precode, which enables the receiver to recover the lost packets...
This paper compares methods of localization in order to try and reduce the processing overhead of optimal multi-lateration whilst still achieving close to its accuracy. Three methods of localization are examined, firstly optimal multi-lateration (OML), which provides the benchmark in terms of accuracy achievable. Secondly sub-optimal blind trilateration (SBT) which randomly selects the minimum feasible...
This paper discusses the efficiency of TCP transmission over a bandwidth-guaranteed network, where the bandwidth for each flow is guaranteed by traffic policing at edge nodes. In particular, it explores a method for improving TCP performance focusing on the size of the buffer to absorb jitter and promote a faster increase in the congestion window size. We propose a rate control method at an edge node...
Wireless sensor networks (WSN) are mainly characterized by dense deployment of sensor nodes. Due to the spatial correlation between sensor nodes and constrained resources of nodes, spatial correlation-based mobile agent routing (SCMAR) algorithm is proposed to exploit such correlation for the realization of advanced efficient mobile agent routing protocol in order to estimate the event with energy...
CICQ(Combined Input-Crosspoint Queued) is a switch fabric with buffers in crosspoints, which brings its nice distributed parallel scheduling property with no internal speedup required. In order to adjust to the nonuniform traffic in the network environment, a novel round-robin scheduling algorithm by using the longest queue detecting (RR-LQD) is proposed. The simulation results show that the RR-LQD...
We consider block transmission techniques combined with rate-1 space time block coding (STBC) for two or four transmit antennas. Since our STBC with 4 transmit antennas is not orthogonal, our receiver includes the cancellation of the residual interference, allowing performances close to the ones of an orthogonal code. We propose an iterative STBC receiver with joint detection and channel estimation...
The bit error rate (BER) performance improvement of single-carrier signal transmissions using one-tap frequency-domain pre-equalization (pre-FDE) is limited by the residual inter-symbol interference (ISI). Recently, we proposed a joint Tomlinson-Harashima precoding (THP) and pre-FDE (called joint THP/pre-FDE) to improve the BER performance by removing the residual ISI. In this paper, to further improve...
A novel OFDM based on-board switching scheme has been proposed, which can achieve service switching by on-board subcarrier switching. This paper focuses on the satellite spot beam downlinks, and proposes a joint optimization method of downlink subcarrier allocation and PAPR reduction. In this method, subcarriers can be allocated adaptively to the services of different user terminals according to the...
The downlink signal in time division synchronous CDMA (TD-SCDMA) system typically has high peak to average power ratio (PAR) due to the multi-code nature of the system. In order to accommodate high peaks, power amplifier (PA) has to operate with considerable back-off, which leads to low operating efficiency. By means of various crest factor reduction (CFR) techniques, the PAR of the transmitted signal...
A modified deterministic structure based carrier frequency offset (CFO) estimation algorithm is presented for the interleaved orthogonal frequency division multiple access (OFDMA) uplink transmission. The presented algorithm combines the conventional deterministic structure algorithm with multiple access interference (MAI) cancellation method so that the estimation performance can be significantly...
UWB is a short range (up to 10 m) wireless communication technology which provides high throughput with low transmission and high reliability. We developed a PHY prototype conformed to ECMA-368, one of UWB standards, and a network simulator for evaluating MAC throughput of ECMA-368. In this paper, we propose an evaluation method considering the characteristic of PHY, the channel model and the propagation...
Wireless ad hoc networks are well suited for use by emergency response teams, for search and rescue operations that require team-based communications in the absence of working telecommunications infrastructure. Unfortunately, wireless ad hoc networks suffer from limited bandwidth and QoS constraints. A proposed explicit multicast (XCAST) based routing protocol (P-XCAST) is presented in this paper...
Programmable FBG-based optical correlators for optical code division multiplexing systems, which are able to change carrier phase of output pulses, are experimentally demonstrated. Phase shifts between adjacent FBGs are tuned thermally with small thermo-electric controllers by PWM signals from a microprocessor. Easy code adaptation with the programmable FBG-based optical correlator is successfully...
Two-cascaded bulk semiconductor optical amplifiers (SOAs) with different bandgaps are proposed as a high-speed all-optical switch based on cross-gain-modulation (XGM) to mitigate the pattern-effect inflicted by a carrier-lifetime-related long-lived gain recovery tail. We numerically analyze the ultrafast gain dynamics in such setup excited by 100 Gbit/s pseudorandom return-to-zero control signal over...
We present a high-speed optical wavelength converter that is capable of converting the data to the same wavelength using a single semiconductor optical amplifier. Error-free wavelength conversion is demonstrated at a bit-rate of 40 Gb/s. The wavelength converter utilizes counter-propagation scheme assisted by blue-detuned optical filtering technology. The counter-propagation configuration eliminates...
Designing optical buffer is still challenge for supporting all optical packet switching. The current practice is to emulate the optical buffer functions through a combination of switch and fiber delay lines (SDL). In this paper we introduce the recent progress on this line, in particular, the SDL-based emulation of optical queues, connectors and buffers.
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