Parallel Decode™

Parallel Decode adds a whole new dimension to the mobile data world by providing two separate data paths between base stations and mobile units. The advanced DSP modems are able to examine two copies of the same message and rebuild missing data. For the user, this means better range using the same number of radio towers and a faster bit rate without having to add infrastructure. It also means faster response times since there is a reduced likelihood of having to retransmit a garbled message due to fading caused by fast moving vehicles and reflected signals.

Parallel Decode technology minimizes the effects of multi-path fading that impedes all forms of wireless communications. Multi-path is a major problem for wireless Public or Private Networks catering to devices that are mobile or portable. The problem exists irrespective of the content, i.e. voice or data. Multi-path fading happens when radio waves arrive at a receiving antenna via multiple paths. The length of these paths vary, thus some signals may take a short and direct route while others are reflected off buildings, natural objects and even moving vehicles. The worst case scenario occurs when all the radio waves arrive via reflected paths. This is common in urban environments where there is no physically unobstructed path between the sending and receiving devices. Radio waves that take different routes can arrive in phase, out of phase, or somewhere in between. Signals that are out of phase decrease the signal strength and may even cause the cancellation of the signal. The effects of multi-path fading can be observed on any wireless device as manifested by clicking sounds and dropouts. Clicking and dropouts are tolerable for wireless voice transmission; but, in the case of wireless data transmission, such effects are intolerable as it either corrupts or destroys the data.

Multi-path fading becomes destructive when cancellation reduces the amplitude of the signal to a level below the receiver’s ability to decode. When the received signal is very strong, fading is not a serious problem. In contrast, where the received signal has deflected off buildings or other physical barriers to reach the receiver, the amplitude is severely reduced. Within a building, signals are attenuated even more since radio waves have trouble penetrating the structure. The wireless communications industry’s tendency to use higher frequencies exacerbates the fading problem. As the frequency of the system increases, the number of multi-path fades experienced by a moving receiver increases proportionately.

Parallel Decode Benefits Increase with Higher Data Rates

As stated above, multi-path fading occurs in all wireless communication networks. In fact, the duration of the fade is similar regardless of a system’s data transmission speed. For this reason the amount of data which is lost or corrupted due to multi-path fading is proportional to the bit rate since the duration of the fade is independent of the bit rate. In other words, the faster the data transmission system the greater the quantity of lost or corrupted data in the event of multi-path fading. Some network protocols attempt to reduce the effects of multi-path fading by adding redundant information to the data being transmitted. Retransmission occurs when the receiver cannot decode the data, using the redundant bits. Redundancy reduces the effective bit rate of the transmission and retransmissions waste valuable airtime that affects the capacity of a communications network. In short, capacity of a network is reduced as the same data is transmitted repetitively.