Messages transmitted to wireless communication devices such as cellular phones are typically encoded, for example, to reduce the chance that noise will corrupt the message. The encoding of the message typically includes adding redundancy (i.e., making the encoded message longer than the original message), introducing symbol dependency (i.e., making the values of each symbol in the encoded message a function of a plurality of bits in the original message), and/or interleaving the message (i.e., mixing the order of the symbols in the encoded message). In the following description and for ease of illustration, a network device that is transmitting a message may be referred to as a transmitter device, while a network device that receives the message may be referred to as a receiver device.
The decoding of the received message at the receiver device is usually performed by finding an original message that would result in the received encoded message with the highest probability. Due to the interleaving and the interdependence of the symbols of the encoded message, the decoding process does not usually begin before the entire message of a predetermined length is received. If the message was not interleaved, some decoding schemes would allow the decoding to begin before the entire message was received and end when the entire message is received. However, such schemes usually have a reduced performance, i.e., a higher rate of failure in correctly decoding the message, in particular in fading channels that are often encountered in practice.
The received message will usually include an error detection code, which is used to determine whether the message was properly decoded. One such code is the cyclic redundancy code (CRC).
Mobile wireless devices, such as cellular phones, typically operate on rechargeable batteries. In order to conserve power, some cellular systems reduce the rate at which the cellular phones consume battery power by having the phones operate in different power consumption modes. For example, such mobile wireless devices may operate in a very low power consuming “idle” mode when such devices are not receiving or transmitting messages or calls. Generally, in the idle mode, the cellular phones deactivate most of their components to reduce their power consumption. Periodically, for example, once every two seconds, the cellular phones will switch from being in an idle mode in which most of their components are deactivated to go into a “partial” wake mode where at least some of their components are activated in order to process paging messages received from a base station of a wireless network. While in the partial wake mode, the base station may send a broadcast or paging message to the cellular phones on a paging channel notifying them to either revert back to the idle mode or to change to a reception or “fully” wake mode, for example in order to receive an incoming call or message. When in a fully wake mode, these mobile wireless devices may be fully powered and most or all of their system components may be fully functional in order to process the incoming call.
The wake-up period for the partial wake mode comprises a warm-up period, a reception period, a decoding period and a shut down period. In the wake-up period the cellular phone activates some or many of its components in order to receive the paging message. Thus, the cellular phone will consume a relatively large amount of power during the wake-up period. If the paging message tells the cellular phone to revert back to the idle mode, the cellular phone shuts down most of its components during the shut down period. Any reduction in the length of the wake-up period results in reducing power consumption and an increase in the time a cellular phone may be used without recharging or replacing its battery.
Because of the large amount of power consumed during the wake-up periods, the amount of time that a cellular phone may remain operational without recharging its batteries may be significantly reduced.