TDMA is more suitable for high throughput data collection than CSMA. Yet, in wireless sensor network plain TDMA-based protocols require complex scheduling. In case of node failures, plain TDMA is hard to recover connection and achieve robust data collection due to the complex scheduling burden. Toward robust data collection, it is important to develop a collection protocol capable of topology adaptability. We have been developing a data gathering protocol named TKN-TWN. TKN-TWN exploits the advantages of TDMA and eases the scheduling burden by using two tokens to arbitrate transmission, providing high throughput via burst data transmission. Moreover, due to the simplified scheduling based on tokens, TKN-TWN is practical to provide adaptability for infrequent topology changes. We enhance the implementation of TKN-TWN over the previous work and carry out experiment on a deployed network in the office room to evaluate the throughput and topology adaptability as well. Experimental results in the network consisting of 32 TinyOS enabled sensor nodes show that TKN-TWN is robust to network changes caused by occasional node failures. Evaluation also shows that TKN-TWN is able to even provide throughput over 10 KByte/s.

To reduce the complexity of scheduling while exploiting the advantages of TDMA-based data collection, we propose TKN-TWN, a token-scheduled multi-channel data collection protocol. The TKN-TWN uses two tokens to arbitrate data-packet transmissions and associates the ownership of tokens with transmission slot assignment. For the reduction of scheduling burden, the TKN-TWN provides topology adaptability while maintaining high throughput in burst data transfer. In this paper, we present the system design of TKN-TWN with enhancement toward topology adaptability based on a previous work. We evaluate TKN-TWN on a local test bed using 31 TelosB sensor nodes. Evaluation results show that the TKN-TWN achieves throughput of 6.4 KByte/s with more than 99% delivery ratio even with occasional node failures.

We present a high throughput data gathering protocol for wireless sensor network. Different from existing works we elaborate a token-scheduled multi-channel TDMA protocol named TKN-TWN that provides better scalability and topology adaptability. TDMA is more suitable for high throughput data collection than CSMA. However, TDMA-based protocols require complex scheduling of the transmission time slot. The scheduling burden is a primary stumbling block of topology adaptability. To ease the scheduling burden while exploiting the advantages of TDMA, we propose to use two tokens arbitrate transmission and associate the ownership of tokens with transmission slot assignment toward throughput optimization. Due to the simplified scheduling based on tokens, TKN-TWN is able to provide scalability and topology adaptability. In addition, TKN-TWN allows burst transmission by leveraging the contention-free nature of TDMA, and sustains high throughput with burst data transmission when sensor nodes have similar traffic pattern. An extensive simulation study indicates that TKN-TWN achieves robust data delivery even in densely deployed large scale sensor networks. Experimental results on Tmote Sky show that TKN-TWN is able to provide throughput over 10 KByte/s, an improvement of about 23% over a prior work.

This paper presents a preambleless communication system to realize industrial wireless control networks (WCN) which are characterized by short payloads and strict real-time requirements. The reduction of the preamble is greatly beneficial for the real-time operation because the transmission time of preambles is longer than that of the short payloads. Our system is implemented on a software defined radio (SDR) platform using GNU Radio toolkit. Experiments show the packet error rate (PER) performance is close to that of the theoretical value in an AWGN (additive white Gaussian noise) environment. Demonstrations show the real-time remote control of inverted pendulums on this system.

Random access process of LTE (long term evolution) system is carried out exploiting the superior correlation property of random access code. Each user unit transmits randomly selected random access code, and the Node B (base station) detects each code by correlating the received signal with all possible random access codes. By comparing the correlation output power to the threshold, randomly selected codes are identified. This paper considers random access process of LTE system in relay network. A problem caused by the introduction of relay network is addressed, and a solution is provided. The proposed solution includes the power control strategy for both downlink broadcast signal and uplink random access signal. Simulation results show that the addressed problem is overcome by the proposed power control algorithm while the backward compatibility is maintained.

Ranging process in IEEE 802.16 system provides a number of functionalities such as initial network entry, uplink synchronization, power adjustment, and system coordination. As the introduction of relay network in IEEE 802.16 systems, a new transmission power control algorithm is necessary. Therefore, this paper proposes a novel ranging transmission power control algorithm which reduces the interference between MS-BS ranging (i.e. ranging between MS and BS) and MS-RS ranging (i.e. ranging between MS and RS). Computer simulation results show the performance of ranging process in terms of ranging detection success probability and validate the efficiency of the proposed transmission power control algorithm. These results will be beneficial as the guideline for the design of IEEE 802.16 relay system.