Wireless sensor networks (WSNs) usually have a regular lattice structure and can be considered as multi-hop multi-route networks. In multi-route transmissions, even if the link quality of several routes decreases, the whole performance of the communication would be compensated by the help of the other routes, which is referred to "the route diversity effect". As generally known, forward error correction (FEC) techniques can enhance the route diversity gain. In this paper, route diversity effect in WSNs using turbo codes is investigated. We introduce a WSN having a triangle lattice structure. BER performances of an additive white Gaussian noise channel and a slow Rayleigh fading channel are evaluated in order to show the route diversity effect.

Recently, sensor networks have been drawing many attentions. The networks can be applicable to many communication systems such as emergency communications, intelligent transportation systems, and so on. They could have a multi-route multi-hop structure by the signal relaying via multiple sensor nodes. Since the wireless links have very severe condition for the communications, a method which can maintain the quality of the links is required. Forward error correction techniques and turbo codes are effective ways to prevent performance degradation by the wireless links. In the multi-hop multi-route structure, the route diversity can be enhanced by using the error correction codes. For the decoding process of the turbo codes, the receiver should estimate the channel information to obtain high decoding performance. Although many channel information estimation methods are not applicable to the multi-hop structure, the channel information estimation method utilizing parity bits can be applied. In this paper, we investigate the route diversity effect of the channel information estimation scheme. We also provide performance comparison between the proposed scheme and the pilot aided scheme. The results suggest that the proposed scheme is effective in obtaining the route diversity.

Multi-hop multi-route networks are promising candidate for achieving the high channel capacity. The networks have high applicability to various new communications. Especially sensor networks are one of the attractive applications of the multihop multi-route networks. When the signals are transmitted over multiple routes, a route diversity effect would be possible. The effect can help to prevent performance degradation caused by quality loss of every route. Forward error correction schemes and turbo coding can be expected to enhance the route diversity. As it would be well known, a turbo encoder generates one message stream and two parity streams and the message stream is more important than the parity streams for reliable communications. Thus by allocating the message stream to a reliable route, the performance degradation could be prevented. In this paper, we examine the effect of the route diversity on multi-hop networks using turbo codes. The diversity effect against the quality loss of the multiple routes is investigated. The results suggest that the multi-route transmissions have high diversity effect. They also suggest that large performance degradation can be prevented by appropriate route assignment of the streams even though the link quality of the multiple routes can not be guaranteed.

For reduction in transmission errors on wireless links, we proposed the multi-route coding on multiple routes for wireless multi-hop networks. In the proposed coding, a source node encodes a packet, divides it into sub packets, and transmits them on multiple routes. A destination node combines and decodes the arriving sub packets to get coding and diversity gain. In this paper, we propose a hybrid ARQ scheme for the multiroute coding. In a hybrid ARQ, important information is firstly transmitted, and redundant information is retransmitted later. On the other hand, in the multiroute coding, all sub packets should have the same importance because of efficient diversity combining. We investigate the trade-off between hybrid ARQ and multi-route coding

In this paper, a system based on pulse spacing modulation and code shift keying is considered. The system uses quadriphase even-shift orthogonal sequences (E-sequences) as orthogonal sequence. The auto-correlation value of the quadriphase sequence is better than that of the biphase E-sequence. In this paper, the probability of block error and efficiency are shown. The probability of block error can improve and the efficiency is greater than that of the SS-PPM system

For reduction in bit errors on wireless channels, we proposed the multi-route coding scheme on multiple routes for wireless multi-hop networks. In this paper, we introduce ARQ to the multi-route coding. In the multi-route coding, the destination node combines and decodes sub packets which are encoded and divided by the source node. The intermediate node relays a sub packet, that is, only a part of a packet. Therefore, the intermediate node cannot detect packet errors, and only the destination node can do after combining and decoding sub packets. We propose the ARQ scheme between the source node and the destination node. We analyze the proposed ARQ scheme and evaluate the throughput performance

One technique to provide high data transmission for large number of users in mobile cellular networks is to arrange the network in a multi-hop structure. Multi-hop networks have large channel capacity and can achieve multi-route transmissions. When the information bit streams are transmitted over multiple routes, a route diversity effect would also be possible. In multiroute transmission, we usually require the routing protocols which can make every route condition be equal. The requirement, however, makes the routing algorithm be complex and causes large power consumption. Forward error correction schemes and turbo coding can be far from the strict requirement although they enhance the effect of route diversity. When applying the turbo codes, the receiver should know the channel condition for iterative decoding. Thus we have to consider how to obtain the channel information over the multi-route multi-hop network. Furthermore, the performance would improve when the destination knows the difference of the route reliability. In this paper, we propose the turbo coded multi-route multi-hop networks using parity check bits. By using parity bits, we can easily estimate the channel information in multi-route multi-hop networks. Using numerical examples we show that the proposed scheme improves the performance in additive white Gaussian noise and slow fading channel conditions

This paper proposes a new initial acquisition method for DS/SS signals with a large carrier frequency offset. In LEO satellite communications, the performance of the initial acquisition is degraded by the effect of a large carrier frequency offset. The proposed method utilizes the property of Walsh functions and is effective against the large carrier frequency offset. The effectiveness of the proposed method is evaluated in terms of mean acquisition time.

The performance of M-ary spread spectrum (M-ary/SS) communication systems is discussed. Firstly, the initial acquisition time is evaluated. Secondly, the retention time, which is the average number of frames holding correct frame timing, and the recovery time, which is the average number of frames required to establish synchronization, are derived. Lastly, the bit-error rate (BER) performance is evaluated. M-ary/SS communication systems, which have more than one spreading code, can improve the BER performance under conditions in which there is additive white Gaussian noise (AWGN). However, the synchronization of M-ary/SS communication systems is difficult because they have several spreading codes. The frame synchronization method uses a Hadamard matrix and "racing counters." As a result, the retention time becomes longer than the recovery time when the size of the lower counter differs greatly from that of the upper counter in the racing counters. Then the BER gets close to the performance which is achieved under complete synchronization.