Eugene Master Traffic Communications Plan

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4.3.3 Wireless Many options exist for low bandwidth wireless systems that do not require FCC licensing to operate. These systems typically operate in the 900 MHz, 2.4 GHz, 4.9 GHz and most recently 5.8 GHz frequency bands. The lower frequency systems (900 MHz) employ Frequency- Hopping Spread Spectrum (FHSS) techniques where the transmitter and receiver rapidly switch frequencies that allow other users to occupy the same frequency band with minimal interference. The higher frequency systems generally support greater bandwidth and are common for Wi -Fi networks, but they utilize a direct sequence technique that does not allow the system to switch frequencies to avoid interference from other users. A wireless radio network can consist of point -to -point or point -to- multipoint systems and some radios allow users to pass IP /Ethernet traffic through the radio. This technology could be considered for local traffic signal interconnect or interconnect from the center to field devices. Figure 9 illustrates an example of wireless communications between a traffic signal and a central server using a remote transceiver at the traffic signal and a master transceiver at the central server that may also be used to communicate with other remote transceivers. Arierra ControNer CaOinat �$ � I I I f x: RS232 � I Si9naCmirroller -- ---------- Transceiver --- -- -- -I Antenna Figure 9. Wireless Example Licensed and unlicensed solutions are available and bandwidths up to 1 Gbps can be achieved, however these systems are very dependent upon line of sight between radios. The lower frequency (900 MHz) systems have the advantage of being able to transmit across greater distances and through some physical interference such as trees, but the bandwidth capability is lower (currently 1 Mbps maximum). To achieve the higher bandwidths supported by the higher frequency systems (2.4 GHz and up), line of sight becomes more critical because these systems are more subject to physical interference from trees and the maximum transmission distance is less. While achieving a bandwidth of 54 Mbps or higher is possible with a wireless solution, the designer must understand the physical properties and constraints associated with the various frequencies to provide an effective design solution. ' In the transportation industry, wireless solutions are commonly used to extend a communications link from the end of a hardwire link (fiber optic cable or copper twisted pair) to a remote intersection or field device as a last mile connection. ' When compared to the high cost of cable installation, properly designed wireless systems can be a viable option. It is expected that they can provide the greatest cost benefit for low speed ' e The 4.9 GHz frequency is reserved for use by emergency services. ' DKS Assoclates Eugene Master Traffic Communications Plan March 2008 Page 24 - - rranscever "Cab)e t I -- — — — — — — — — Genital Server l — — — — — — — — — t Figure 9. Wireless Example Licensed and unlicensed solutions are available and bandwidths up to 1 Gbps can be achieved, however these systems are very dependent upon line of sight between radios. The lower frequency (900 MHz) systems have the advantage of being able to transmit across greater distances and through some physical interference such as trees, but the bandwidth capability is lower (currently 1 Mbps maximum). To achieve the higher bandwidths supported by the higher frequency systems (2.4 GHz and up), line of sight becomes more critical because these systems are more subject to physical interference from trees and the maximum transmission distance is less. While achieving a bandwidth of 54 Mbps or higher is possible with a wireless solution, the designer must understand the physical properties and constraints associated with the various frequencies to provide an effective design solution. ' In the transportation industry, wireless solutions are commonly used to extend a communications link from the end of a hardwire link (fiber optic cable or copper twisted pair) to a remote intersection or field device as a last mile connection. ' When compared to the high cost of cable installation, properly designed wireless systems can be a viable option. It is expected that they can provide the greatest cost benefit for low speed ' e The 4.9 GHz frequency is reserved for use by emergency services. ' DKS Assoclates Eugene Master Traffic Communications Plan March 2008 Page 24