Network elements, wireless communication system and methods therefor
An Access Point ( 105 ) serving a small cell ( 202 ) in a cellular communication system ( 100 ) uses the User Equipment intra-frequency Primary Scrambling Code detection mode to detect neighbors inter-frequency by switching its carrier frequency to a frequency on which it is desired to check for neighbors (for a period long enough and/or often enough for it UE to have a reasonable chance of detecting such a neighbor). Received measurements on such neighbor cells ( 202, 203 ) may be used to compile a neighbor cell list if no such list has been preconfigured in the Access Point or if network listen results have provided only a limited number of detected neighbor cells.
1. A method for detecting neighbour cells in a wireless communication system which comprises a first cell served by a network element and at least one neighbouring cell, the method comprising, at the network element:
(a) allocating a set of operating frequencies for the network element,
(b) selecting an operating frequency for the network element from the set of allocated operating frequencies,
(c) transmitting an instruction to a wireless communication unit located in the first cell to enter an intra-frequency detection mode and send intra-frequency measurement reports relating to neighbour cells that are operating on the selected operating frequency used by the network element, and receiving and storing said intra-frequency measurement reports,
(d) after a predetermined time period has elapsed, switching to another operating frequency from the set of allocated operating frequencies to receive further intra-frequency measurement reports, and
(e) receiving said further intra-frequency measurement reports from the wireless communication unit relating to neighbour cells that are operating on said another operating frequency, and storing said further intra-frequency measurement reports.
2. The method of claim 1 , including; repeating steps (d) and (e) until all operating frequencies included in the set have been selected.
3. The method of claim 1 , wherein selecting another operating frequency for the network element from the set is co-incident with a commencement of a network listen session performed at the network element.
4. The method of claim 1 , wherein at the network element, transmitting a message to the wireless communication unit including information relating to an imminent change in operating frequency.
5. The method of claim 4 , wherein the message transmitted to the wireless communication unit comprises a handover message.
6. The method of claim 4 , wherein the message transmitted to the wireless communication unit comprises a cell selection System Information message.
7. The method of claim 4 , wherein the message transmitted to the wireless communication unit comprises a cell reselection System Information message.
8. The method of claim 1 , further comprising configuring the network element with:
a first set of frequencies, from which the network element is allowed to select an operating frequency for wireless communication;
a second set of frequencies for scanning for inter-frequency neighbour cells; and
the set of allocated operating frequencies, each frequency in the set of allocated operating frequencies being a frequency which the network element is allowed to use temporarily as an operating frequency for scanning for intra-frequency neighbour cells.
9. The method of claim 8 , wherein,
prior to selecting an operating frequency for the network element from the set of allocated operating frequencies, the network element runs a network listen session by scanning frequencies in the second set of frequencies to discover inter-frequency neighbour cells, and:
when sufficient neighbours are found during the network listen session, then the network element selects an operating frequency from the first frequency set and continues with wireless communication on that frequency; or
when insufficient or no neighbours are found during the network listen session, then the network element selects the operating frequency from the set of allocated operating frequencies to use temporarily as an operating frequency for scanning for intra-frequency neighbour cells.
10. A tangible computer program product having an executable computer program code stored thereon for execution by a processor to perform a method of detecting neighbour cells in a wireless communication system which comprises a first cell served by a network element and at least one neighbouring cell, the method comprising, at the network element:
(a) allocating a set of operating frequencies for the network element,
(b) selecting an operating frequency for the network element from the set of allocated operating frequencies,
(c) transmitting an instruction to a wireless communication unit located in the first cell to enter an intra-frequency detection made and send intra-frequency measurement reports relating to neighbour cells that are operating on the selected operating frequency used by the network element, and receiving and storing said intra-frequency measurement reports,
(d) after a predetermined time period has elapsed, switching to another operating frequency from the set of allocated operating frequencies to receive further intra-frequency measurement reports, and
(e) receiving said further intra-frequency measurement reports from the wireless communication unit relating to neighbour cells that are operating on said another operating frequency, and storing said further intra-frequency measurement reports.
11. The tangible computer program product of claim 10 , comprising at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, an Electrically Erasable Programmable Read Only Memory and a Flash memory.
12. A network element for supporting communications in a wireless communication system which includes a first cell served by the network element and at least one neighbouring cell, wherein the network element comprises:
a signal processor arranged to select a first operating frequency for the network element from a predefined set of operating frequencies, and
a transmitter arranged to transmit an instruction to a wireless communication unit located in the first cell to enter an intra-frequency detection mode and send intra-frequency measurement reports relating to neighbour cells that are operating on the selected operating frequency used by the network element,
a receiver arranged to receive said intra-frequency measurement reports; and
a store arranged to store said received intra-frequency measurement reports,
wherein
the network element is arranged, after a predetermined period of time, to switch to another operating frequency from the set of allocated operating frequencies to receive further intra-frequency measurement reports, the another operating frequency being different from the first operating frequency, and
the receiver is further arranged to receive said further intra-frequency measurement reports from the wireless communication unit, of neighbouring cells that are operating either on the first frequency or at least one subsequent frequency, and
the store is arranged to store said received further intra-frequency measurement reports.
13. The network element of claim 12 , wherein the signal processor is implemented in one or more integrated circuits.
14. A wireless communication system comprising a network element as claimed in claim 12 .