In CCT, a cluster of two or more physically separated relays (radios) transmit at the same time to emulate a transmit diversity array. Figure 1 shows the basic CCT topology, consisting of a source, a cluster of relays, and a destination. The objective is for a message to be delivered from the source node to the destination node; however, the destination is out of range of the source, so the source transmits to the relays, and then the relays forward the message to the destination. The number inside the destination triangle represents how many relays participate in the cooperative transmission. The destination could be a Sink or Gateway node that connects a wireless sensor network to the internet, a wireless LAN access point, or a cellular base station. The relays synchronize their transmissions based on a packet received by the source transmitter. The extra power from the combined relay waveforms enables penetration through barriers and extension of the range. SARL has recently achieved what appears to be the first demonstration of practical CCT. Figure 2 shows some range extension results obtained in the Centergy Building. The magnified photo shows the four software defined radios (SDRs) that form the relay cluster, which is in the same room as the source. The red triangles show potential destinations. Let a node being “reached” mean that its packet error rate (PER), averaged over multipath fading realizations, is <10%. The red triangle with the “4” can be reached only when all four relays are used.
- Yong Jun Chang and Mary Ann Ingram, “Cluster Transmission Time Synchronization for Cooperative Transmission using Software Defined Radio,” to be presented at the IEEE International Conference on Communications (ICC) Workshop on Cooperative and Cognitive Mobile Networks (CoCoNet3), June 2010
- Yong Jun Chang, Haejoon Jung, and Mary Ann Ingram, “Demonstration of a New Degree of Freedom in Wireless Routing: Concurrent Cooperative Transmission,” HotEMNETS 2010 Workshop on Hot Topics in Embedded Networked Sensors, Killarney, Ireland, June 28-29 2010.
- Haejoon Jung, Yong Jun Chang, and Mary Ann Ingram, “Experimental Range Extension of Concurrent Cooperative Transmission in Indoor Environments at 2.4GHz,” to be presented at MILCOM 2010.
Last revised on Jan,28,2010.