TurboCell Hidden Node Support

Most protocols for transmitting packets over a wireless medium use some form of CSMA/CA, or "Carrier Sense Multiple Access/Collision Avoidance." The main problem with this method for transmitting over a wireless link is that all stations on the wireless network must be able to "hear" each others' packets, or performance may decrease substantially.

In real-life situations, stations are generally not able to communicate directly with every other station in the wireless network, and collision avoidance is a hit-or-miss proposition. This inability to hear other remote stations' traffic can be caused by bands of interference between stations, long distances between stations, or physical obstructions such as walls, trees, or buildings. Hidden nodes are common in indoor and outdoor networks, and have an especially great impact on performance of most outdoor Point-to-Multipoint networks.

Even when specifically accounted for, most standard radio systems do not efficiently handle the problem of hidden network nodes. The IEEE 802.11 protocol standard uses an Request To Send/Clear To Send mechanism to decrease the effect of the hidden node problem, but the IEEE study on The Effect of Hidden Terminals on the Performance of the IEEE 802.11 MAC Protocol documents for the 802.11 protocol states that "Although throughput is acceptable when about 10 percent of station pairs are hidden, packet delay can increase by an order of magnitude. Performance of the protocol drops sharply when the number of hidden pairs exceeds 10 percent."

TurboCell drastically reduces the problems associated with hidden nodes by centralizing access to the wireless medium at the TurboCell Base Station. Instead of acting as a contention-based network, TurboCell dynamically allocates bandwidth between the remote stations, optimizing throughput between stations while still preventing one station from monopolizing air time. Even if every remote station is hidden from every other satellite station, as is often the case in outdoor networks with satellites using directional antennas, a TurboCell network still offers excellent performance.

For more information about TurboCell's technical superiority for outdoor Point-to-Multipoint networks, including Adaptive Dynamic Polling the benefits associated with it, please visit our page on TurboCell.