#### Example 2.1 | #### Question 2.6 Question 2.7

## Example: 8-ary signalling

#### The purpose of using multi-level or multi-symbol signalling is to allow the designer to trade channel capacity with bandwidth and noise immunity. Consider, for example, a system employing eight voltage states rather than a simple binary two-state design.

| #### Trace A represents the binary data source to be encoded into the 8-ary signal. #### Trace B is the encoded signal with the information rate kept the same for both binary and 8-ary systems. The result is that the rate at which the voltage state is varied on the channel is reduced by a factor of three. This translates directly into a threefold reduction in bandwidth required to support communication. #### Finally, trace C shows an 8-ary signal which has the same symbol rate as the binary source and hence requires the same bandwidth, but the information rate has been increased threefold.