Efficient request access for OFDM systems

In a digital communication system employing a shared medium, a method for operating a central access point to receive requests for access to said shared medium, said method comprising:

• receiving an OFDM burst of time domain symbols;
• converting said OFDM burst of time domain symbols into frequency domain symbols;
• differentially decoding said frequency domain symbols;
• obtaining access requests from multiple subscriber units;
• and
• providing a phase descrambling code that specifies phase shifts for frequency domain positions within said OFDM burst;
• and
• applying said phase shifts of said phase descrambling code to said frequency domain symbols according to positions of said frequency domain symbols.

In a digital communication system employing a shared medium, a method for operating a selected data communication device to request access to said shared medium, said method comprising:

• forming frequency domain symbols of an OFDM burst, wherein a first group of frequency domain symbols comprise non-zero values and a second group of frequency domain symbols comprise zero values to reserve said second group for data transmitted by other data communication devices, said first group of frequency domain symbols being contiguous to one another;
• transforming said frequency domain symbols of said OFDM burst into time domain symbols;
• and
• transmitting said time domain symbols as a request for access to said shared medium.

In a digital communication system employing a shared medium, a method for operating a central access point to receive requests for said shared medium, said method comprising:

• receiving an OFDM burst of time domain symbols;
• converting said OFDM burst of time domain symbols into frequency domain symbols;
• obtaining from a first subgroup of said frequency domain symbols a first request for access to said shared medium from a first subscriber unit, wherein frequency domain symbols of said first subgroup are contiguous to one another;
• and
• obtaining from a second subgroup of said frequency domain symbol a second request for access to said shared medium from a second subscriber unit, wherein frequency domain symbols of said second subgroup are contiguous to one another.

In a digital communication system employing a shared medium, apparatus for operating a selected data communication device to request access to said shared medium, said apparatus comprising:

• a burst forming system that forms frequency domain symbols of an OFDM burst, wherein a first group of frequency domain symbols comprise differentially encoded data and a second group of frequency domain symbols comprise zero values to reserve said second group for data transmitted by other subscriber units;
• a converter that transforms said frequency domain symbols of said OFDM burst into time domain symbols;
• and
• a transmitter system that transmits said time domain symbols as a request for access to said shared medium.

In a digital communication system employing a shared medium, apparatus for operating a central access point to receive requests for access to said shared medium, said apparatus comprising:

• a receiver system that receives an OFDM burst of time domain symbols;
• a converter that converts said OFDM burst of time domain symbols into frequency domain symbols, groups of said frequency domain symbols resulting from transmissions by multiple subscriber units;
• a differential decoder that differentially decodes said frequency domain symbols;
• and
• a phase descrambling block that provides a phase descrambling code that specifies phase shifts for frequency domain positions within said OFDM burst;
• and
• a phase rotator that applies said phase shifts of said phase descrambling code to said frequency domain symbols according to positions of said frequency domain symbols.

In a digital communication system employing a shared medium, apparatus for operating a selected data communication device to request access to said shared medium, said apparatus comprising:

• a burst forming system that forms frequency domain symbols of an OFDM burst, wherein a first group of frequency domain symbols comprise non-zero values and a second group of frequency domain symbols comprise zero values to reserve said second group for data transmitted by other data communication devices, said first group of frequency domain symbols being contiguous to one another;
• a converter that transforms said frequency domain symbols of said OFDM burst into time domain symbols;
• and
• a transmitter system that transmits said time domain symbols as a request for access to said shared medium.

In a digital communication system employing a shared medium, apparatus for operating a central access point to receive requests for access to said shared medium, said apparatus comprising:

• a receiver system that receives an OFDM burst of time domain symbols;
• a converter that converts said OFDM burst of time domain symbols into frequency domain symbols;
• and
• a selector that obtains from a first subgroup of said frequency domain symbols a first request for access to said shared medium from a first subscriber unit, wherein frequency domain symbols of said first subgroup are contiguous to one another, and that obtains from a second subgroup of said frequency domain symbol a second request for access to said shared medium from a second subscriber unit, wherein frequency domain symbols of said second subgroup are contiguous to one another.

In a digital communication system employing a shared medium, a method for operating a selected data communication device to request access to said shared medium, said apparatus comprising:

• means for forming frequency domain symbols of an OFDM burst, wherein a first group of frequency domain symbols comprise differentially encoded data and a second group of frequency domain symbols comprise zero values to reserve said second group for data transmitted by other subscriber units;
• means for transforming said frequency domain symbols of said OFDM burst into time domain symbols;
• and
• means for transmitting said time domain symbols as a request for access to said shared medium.

In a digital communication system employing a shared medium, a method for operating a selected data communication device to request access to said shared medium, said apparatus comprising:

• means for forming frequency domain symbols of an OFDM burst, wherein a first group of frequency domain symbols comprise non-zero values and a second group of frequency domain symbols comprise zero values to reserve said second group for data transmitted by other data communication devices, said first group of frequency domain symbols being contiguous to one another;
• means for transforming said frequency domain symbols of said OFDM burst into time domain symbols;
• and
• means for transmitting said time domain symbols as a request for access to said shared medium.

In a digital communication system employing a shared medium, apparatus for operating a central access point to receive requests for said shared medium, said apparatus comprising:

• means for receiving an OFDM burst of time domain symbols;
• means for converting said OFDM burst of time domain symbols into frequency domain symbols;
• means for obtaining from a first subgroup of said frequency domain symbols a first request for access to said shared medium from a first subscriber unit, wherein frequency domain symbols of said first subgroup are contiguous to one another;
• and
• means for obtaining from a second subgroup of said frequency domain symbol a second request for access to said shared medium from a second subscriber unit, wherein frequency domain symbols of said second subgroup are contiguous to one another.