System and method for providing contention channel organization for broadband satellite access in a communications network
View Patent ↗Two types of contention channels are used to accommodate broadband packet data in a satellite communication network. A first contention channel is used by unsynchronized user terminals to access the system and request a traffic channel. The first contention channel is of a sufficient duration to accommodate a RACH message, as well as the timing uncertainty between user terminals within a given spot beam. A second contention channel is shorter in duration than the first contention channel, and is narrowband, so that more than one second contention channel may be transmitted within the bandwidth of the broadband traffic channels. The second contention channels are used by synchronized user terminals for transmitting packet RACH, or PRACH, messages. The more efficient nature of the PRACH channels accommodates the increased overhead associated with bursty packet data, without the capacity cost of the longer duration RACH channel.
1. A wireless radio terminal for transmitting and receiving packets over a wireless network, comprising:
a first access request signal generator for generating a first access request signal; and
a second access request signal generator for generating a second access request signal; and
wherein said first access request signal generator is adapted to transmit said first access request signal on a first channel, said first channel having a duration equal at least to the duration of said first access request signal plus a maximum timing uncertainty between unsynchronized terminals; and
wherein said second access request signal generator is adapted to transmit said second access request signal on a second channel within a second window having a duration less than the duration of said first window; and
wherein said second channel has a duration equal to an integer number of time slots, and said second channel is within the frequency range associated with traffic channels; and
wherein said second channel has a bandwidth less than one half of the bandwidth of said traffic channels.
2. A wireless network having a plurality of broadband channels, a first contention channel having a duration equal at least to the duration of a RACH message plus a maximum timing uncertainty, and a second contention channel having a duration which is less than the duration of said first contention channel;
wherein said second contention channel is within the frequency range associated with traffic channels; and
wherein said second contention channel has a bandwidth less than one half of the bandwidth of said traffic channels.
3. A wireless network having a plurality of broadband channels, a first contention channel having a duration equal at least to the duration of a RACH message plus a maximum timing uncertainty, and a second contention channel having a duration which is less than the duration of said first contention channel;
wherein said second contention channel is within the frequency range associated with traffic channels; and
wherein said second contention channel has a bandwidth less than one third of the bandwidth of said traffic channels.
4. A wireless network having a plurality of broadband channels, a first contention channel having a duration equal at least to the duration of a RACH message plus a maximum timing uncertainty, and a second contention channel having a duration which is less than the duration of said first contention channel;
wherein said second contention channel is within the frequency range associated with traffic channels; and
wherein said second contention channel has a bandwidth less than one fourth of the bandwidth of said traffic channels.
5. A method of transmitting access request signals in a wireless network, said method comprising the steps of:
receiving a beacon signal from said network identifying a time frame,
dividing a communication channel into a plurality of subchannels, said channel having a continuous range of frequencies,
transmitting a first electromagnetic signal in a first one of said plurality of subchannels during a first of a plurality of time slots, said first electromagnetic signal having a duration less than one of said time slots,
abstaining from transmitting electromagnetic signals on said first subchannel during at least a second of said plurality of time slots,
receiving timing correction information from said network,
based on said timing correction information, transmitting a second electromagnetic signal in a second one of said plurality of subchannels during a third of said plurality of time slots, said second electromagnetic signal having a duration less than one of said time slots,
receiving traffic channel assignment data from said network, said traffic channel assignment containing data representing a particular time slot,
transmitting data during said particular time slot on a traffic channel comprising a continuous set of frequencies allocated to said subchannels.