Signaling of random access preamble parameters in wireless networks
User equipment (UE)-initiated accesses within a cellular network are optimized to account for cell size and to reduce signaling overhead. A fixed set of preamble parameter configurations for use across a complete range of cell sizes within the cellular network is established and stored within each UE. A UE located in a given cell receives a configuration number transmitted from a nodeB serving the cell, the configuration number being indicative of a size of the cell. The UE selects a preamble parameter configuration from the fixed set of preamble parameter configurations in response to the received configuration number and then transmits a preamble from the UE to the nodeB using the preamble parameter configuration indicated by the configuration number.
1. A method for transmitting a preamble, comprising:
maintaining a fixed set of preamble parameter configurations, each of the preamble parameter configurations corresponding to a respective cyclic shift value;
receiving at a user equipment (UE) a configuration number;
selecting, by the UE, a preamble parameter configuration specified by the received configuration number from the fixed set of preamble parameter configurations; and
transmitting, by the UE, a preamble using the selected preamble parameter configuration.
2. The method of claim 1 , wherein each preamble parameter configuration of the set of preamble parameter configurations implicitly defines a number of root sequences and a number of cyclic shifts per root sequence.
3. The method of claim 2 , wherein the fixed set of preamble parameter configurations comprises no more than sixteen preamble parameter configurations.
4. The method of claim 2 , wherein transmitting a preamble comprises:
determining a number of root sequences and a number of cyclic shifts of the selected preamble parameter configuration;
mapping a predetermined number of preamble signatures to subsequent cyclic shifts of a given root sequence according to the number of cyclic shifts until the given root sequence is full, for all of the number of root sequences until a last root sequence;
adjusting a number of cyclic shifts mapped onto the last root sequence such that the predetermined number of preamble signatures are mapped; and
selecting one of the mapped preamble signatures for use in transmitting the preamble.
5. The method of claim 4 , wherein the predetermined number of preamble signatures is sixty-four.
6. The method of claim 1 , wherein the fixed set of preamble parameter configurations sample the continuous cell size range covered by a cellular network in a non-linear way, such that a finer configuration granularity is provided for smaller cells, whereby a broader deployment of smaller cells compared to larger cells is better supported.
7. A user equipment (UE), comprising:
means for storing a fixed set of preamble parameter configurations, each of the preamble parameter configurations corresponding to a respective cyclic shift value;
means for receiving information indicative of a particular preamble parameter configuration from the fixed set of preamble parameter configurations;
means for selecting a preamble parameter configuration from the fixed set of preamble parameter configurations based on the received information; and
means for transmitting a preamble using the selected preamble parameter configuration.
8. The UE of claim 7 , wherein each preamble parameter configuration of the set of preamble parameter configurations implicitly defines a number of root sequences and a number of cyclic shifts per root sequence.
9. The UE of claim 8 , wherein the fixed set of preamble parameter configurations comprises no more than sixteen preamble parameter configurations.
10. The UE of claim 8 , wherein the means for transmitting a preamble comprises:
means for determining a number of root sequences and a number of cyclic shifts of the selected preamble parameter configuration;
means for mapping a predetermined number of preamble signatures to subsequent cyclic shifts of a given root sequence according to the number of cyclic shifts until the given root sequence is full, for all of the number of root sequences until a last root sequence;
means for adjusting a number of cyclic shifts mapped onto the last root sequence such that the predetermined number of preamble signatures are mapped; and
means for selecting one of the mapped preamble signatures for use in transmitting the preamble.
11. The UE of claim 10 , wherein the predetermined number of preamble signatures is sixty-four.
12. The UE of claim 7 , wherein the fixed set of preamble parameter configurations sample the continuous cell size range covered by a cellular network in a non-linear way, such that a finer configuration granularity is provided for smaller cells, whereby a broader deployment of smaller cells compared to larger cells is better supported.
13. A user equipment (UE), comprising:
a receiver configured to receive information indicative of a particular configuration number of a fixed set of preamble parameter configurations, each of the preamble parameter configurations corresponding to a respective cyclic shift value;
a processor configured to select a preamble parameter configuration from the fixed set of preamble parameter configurations based on the received information; and
a transmitter connected to the processor and configured to transmit a signal using the selected preamble parameter configuration.
14. The UE of claim 13 , wherein each preamble parameter configuration of the set of preamble parameter configurations implicitly defines a number of root sequences and a number of cyclic shifts per root sequence.
15. The UE of claim 14 , wherein the fixed set of preamble parameter configurations comprises no more than sixteen preamble parameter configurations.
16. The UE of claim 14 , wherein the transmitter comprises:
circuitry for determining a number of root sequences and a number of cyclic shifts of the selected preamble parameter configuration;
circuitry for mapping a predetermined number of preamble signatures to subsequent cyclic shifts of a given root sequence according to the number of cyclic shifts until the given root sequence is full, for all of the number of root sequences until a last root sequence;
circuitry for adjusting a number of cyclic shifts mapped onto the last root sequence such that the predetermined number of preamble signatures are mapped; and
circuitry for selecting one of the mapped preamble signatures for use in transmitting the preamble.
17. The UE of claim 16 , wherein the predetermined number of preamble signatures is sixty-four.
18. The UE of claim 13 , wherein the fixed set of preamble parameter configurations sample the continuous cell size range covered by a cellular network in a non-linear way, such that a finer configuration granularity is provided for smaller cells, whereby a broader deployment of smaller cells compared to larger cells is better supported.