GB2415326A - Downlink signalling to a terminal in soft handover - Google Patents
Downlink signalling to a terminal in soft handover Download PDFInfo
- Publication number
- GB2415326A GB2415326A GB0413443A GB0413443A GB2415326A GB 2415326 A GB2415326 A GB 2415326A GB 0413443 A GB0413443 A GB 0413443A GB 0413443 A GB0413443 A GB 0413443A GB 2415326 A GB2415326 A GB 2415326A
- Authority
- GB
- United Kingdom
- Prior art keywords
- base station
- terminal
- likelihood
- signalling
- downlink
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000011664 signaling Effects 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 23
- 230000005540 biological transmission Effects 0.000 claims abstract description 19
- 101000741965 Homo sapiens Inactive tyrosine-protein kinase PRAG1 Proteins 0.000 description 4
- 102100038659 Inactive tyrosine-protein kinase PRAG1 Human genes 0.000 description 4
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/22—TPC being performed according to specific parameters taking into account previous information or commands
- H04W52/221—TPC being performed according to specific parameters taking into account previous information or commands using past power control commands
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- H04Q7/3818—
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/382—Monitoring; Testing of propagation channels for resource allocation, admission control or handover
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
-
- H04Q2007/3844—
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/16—Performing reselection for specific purposes
- H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
Abstract
A method of downlink signalling to a terminal (4) in soft handover, from one or more of a plurality of base-stations (1, 2, 3), wherein the or each base station makes independent downlink transmissions, the method comprising assessing the likelihood of another base station having a better link to the terminal; and only transmitting a message to the terminal, if the likelihood of another base station having a better link is below a predetermined value.
Description
241 5326
A METI IOD OF DOWNLINK SIGNALLING TO A TERMINAL IN SOFT
HANDOVER
This invention relates to a method of downlink signalling to a terminal in soft handover, in particular for 3r generation mobile phone systems.
A significant issue for enhanced dedicated channel (E-DCH) is the support of hybrid automatic repeat request (HARQ) in soft handover (SI-IO). In SHO, each node B must send an acknowledgement or no acknowledgment (ACK/NACK) indication to a user equipment (UE). However some node Bs may suffer poor downlink conditions, with the result that ACK/NACK signalling may require a more significant amount of downlink power.
In accordance with a first aspect of the present invention, a method of downlink signalling to a terminal in soft handover, from one or more of a plurality of base stations, wherein the or each base station makes independent downlink transmissions, comprises assessing the likelihood of another base station having a better link to the terminal; and only transmitting a message to the terminal, if the likelihood of another base station having a better link is below a predetermined value.
Preferably, the message is a response message relating to an uplink transmission made by the terminal and received at the or each base station.
Preferably, the base station assesses the likelihood of another base station having a better link by analysing signals sent to that terminal in a specific time interval and the response of the terminal to those signals.
Preferably, the analysed signals include at least one of power control commands sent to the terminal and hybrid repeat request transmission acknowledgments.
Alternatively, the base station assesses the likelihood of another base station having a better link by analysing properties of signals received from that terminal in a specific time interval.
In this case, preferably, the analysed properties include at least one of received signal power and received signal to noise ratio.
Preferably, the predetermined threshold value of the likelihood of another base station having a better link that may be used in deciding whether to make a DL transmission is set by signalling from a control entity.
ce. :e ct: cee: . . Prcfcrably, the assessment of likelihood further comprises comparing a power required to send a response message with a predetermined power Icvel; and only sending the response message, if the power required is below this level.
Prcterably, the predetermined power level is set either by analysis of power required by the base station to serve other terminals or to transmit other messages to the same terminal, or is set by signalling from a control entity.
The response message can take various forms, typically acknowledgments, but preferably, the response message comprises a hybrid automatic repeat request (ARQ) I O acknowledgment.
Preferably, the base station is one of a Node B or RNC.
In accordance with a second aspect of the present invention, a base station, for a communication system, is adapted to carry out the method of the first aspect.
In accordance with a third aspect of the present invention, a communication system comprising at least one base station according to the second aspect, further comprises a terminal and at least one data channel.
Preferably, the terminal comprises one of a mobile phone, a laptop, a PC card or a personal digital assistant.
An example of a method of downlink signalling in soft handover in accordance with the present invention will now be described in which: Figure 1 illustrates a typical arrangement of a terminal and base station to which the method of the present invention is applied.
Fig. 1 illustrates a situation in which the method of the present invention is applicable. Three different base stations or node B's 1, 2, 3 receive signals from a terminal, or user equipment (UK) 4. There are different path loss distances between the base stations and the terminals. In this example, base station 2 has the least path loss distance, base station 1 is not much larger and base station 3 has a significant path loss distance and so is least likely to receive a transmission successfully and also needs to use the most power to send an acknowledgment. When the terminal 4 transmits data it expects to receive at least one acknowledgment that the data has been safely received.
Without this the terminal is likely to retransmit the same information, rather than transmit new data. The base stations do not wish to use power unnecessarily in ce ee cel :: 't. ':e ce:: :: . c acknowledging, if they do not have the best link to the terminal. One way of avoiding unnecessary acknowledgment is to use unipolar ACK/NACK signalling for some cells in an active set (AS). Thus, NACK is signalled by using discontinued transmission (DTX), i.e. not signalling anything, whilst ACK is indicated by a suitable transmission.
This saves power of node Bs for which the block error rate (BLER) is higher.
One way to manage the node B resources is for each node B 1, 2, 3 to examine the power control commands it has sent to the terminal 4 over a pre-set interval and the signal to interference ratio (SIR) level of each HARQ retransmission. If the node B has sent a lot of power up commands that have been ignored, and if the SIR is much lower than the target for several of the retransmissions, the node B may assume that another node B has a better path and is more likely to detect the transmission. The node B may also examine the number of successfully received blocks it has recently decoded.
Another parameter which can be taken into account is whether the UE data rate, and hence potentially wasted noise rise is significant When the node B successfully decodes a transmission, it examines its downlink power budget and if the node B has determined that another node B is more likely to detect the transmission, and that the percentage of power required for making a downlink ACK transmission is higher than some pre- set limit, then the node B may autonomously decide not to send an ACK. . This is equivalent to dynamically varying the active set size according to perceived instantaneous usefulness of a node B in the active set and the downlink resource situation.
Although one example has been described above, the present invention applies to any situation where a terminal is in SHO with ON/OFF signalling but the form of downlink signalling is specific to the node B and hence does not benefit from macrodiversity gain and a node B has the option to use discontinued transmission signalling,. If the transmitted downlink signalling is a response to an uplink transmission that is in SHO, the effect of the method is to dynamically vary the active set size. c
Claims (15)
1. A method of downlink signalling to a terminal in soft handover, from one or more of a plurality of base-stations, wherein the or each base station makes independent downlink transmissions, the method comprising assessing the likelihood of another base station having a better link to the terminal; and only transmitting a message to the terminal, if the likelihood of another base station having a better link is below a predetermined value.
2. A method according to claim l, wherein the message is a response message relating to an uplink transmission made by the terminal and received at the or each base stations.
t 5
3. A method according to claim l or claim 2, wherein the base station assesses the likelihood of another base station having a better link by analysing signals sent to that terminal in a specific time interval and the response of the terminal to those signals.
4. A method according to claim 3, wherein the analysed signals include at least one of power control commands sent to the terminal and hybrid repeat request transmission acknowledgments.
5. A method according to claim l or claim 2, wherein the base station assesses the likelihood of another base station having a better link by analysing properties of signals received from that terminal in a specific time interval.
6. A method according to claim 5, wherein the analysed properties include at least one of received signal power and received signal to noise ratio.
7. A method according to any preceding claim, wherein the predetermined threshold value of the likelihood of another base station having a better link that may be used in deciding whether to make a downlink transmission is set by signalling from a control entity.
# # # # # # ^ # c. e #do e s
8. A method according to any preceding claim, wherein the assessment further comprises comparing a power required to send a response message with a predetermined power level; and only sending the response message, if the power required is below this level.
9. A method according to claim 8, wherein the predetermined power level is set by analysis of power required by the base station to serve other terminals or to transmit other messages to the same terminal, or is set by signalling from a control entity.
10. A method according to any preceding claim, wherein the response message comprises a hybrid automatic repeat request (ARQ) acknowledgment.
11. A method according to any preceding claim, wherein the base station is one of a Node B or RNC.
12. A base station, for a communication system, the base station being adapted to carry out the method of any preceding claim.
13. A communication system comprising at least one base station according to claim 12, the system further comprising a terminal and at least one data charmer.
14. A system according to claim 13, wherein the terminal comprises one of a mobile phone, a laptop, a PC card or a personal digital assistant.
15. A method of downlink signalling to a terminal in soft handover, from one or more of a plurality of base-stations, wherein the or each base station makes independent downlink transmissions as hereinbefore described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0413443A GB2415326B (en) | 2004-06-16 | 2004-06-16 | A method of downlink signalling to a terminal in soft handover |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0413443A GB2415326B (en) | 2004-06-16 | 2004-06-16 | A method of downlink signalling to a terminal in soft handover |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0413443D0 GB0413443D0 (en) | 2004-07-21 |
| GB2415326A true GB2415326A (en) | 2005-12-21 |
| GB2415326B GB2415326B (en) | 2006-06-21 |
Family
ID=32749999
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0413443A Expired - Fee Related GB2415326B (en) | 2004-06-16 | 2004-06-16 | A method of downlink signalling to a terminal in soft handover |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2415326B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007069948A1 (en) * | 2005-12-14 | 2007-06-21 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for reducing uplink traffic load on transport network at basestation during soft handover. |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0671819A2 (en) * | 1994-03-10 | 1995-09-13 | Roke Manor Research Limited | Power control for mobile phone during soft handoff between two base stations using power control bits |
-
2004
- 2004-06-16 GB GB0413443A patent/GB2415326B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0671819A2 (en) * | 1994-03-10 | 1995-09-13 | Roke Manor Research Limited | Power control for mobile phone during soft handoff between two base stations using power control bits |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007069948A1 (en) * | 2005-12-14 | 2007-06-21 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for reducing uplink traffic load on transport network at basestation during soft handover. |
| US8010115B2 (en) | 2005-12-14 | 2011-08-30 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for reducing uplink traffic load on transport network at basestation during soft handover |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0413443D0 (en) | 2004-07-21 |
| GB2415326B (en) | 2006-06-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20080616 |
|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) |
Free format text: REGISTERED BETWEEN 20090205 AND 20090211 |