ES2358640T3 - PROCEDURE TO ASSIGN WALSH SPACE IN A COMMUNICATIONS SYSTEM. - Google Patents

Abstract

A method for allocating Walsh space in a communications system, comprising: receiving (1020) in a mobile station, from a base station, an indicator of the Walsh space through a Walsh space indicator channel, in the which the Walsh space indicator channel is a multiplexed code division channel, transmitted continuously, to communicate a Walsh space indicator, the Walsh space indicator specifying a number of Walsh functions from a list of programmed Walsh functions; receive, on the mobile station, from the base station, coded messages, in which the messages are coded using an encoder at the base station, initialized with the Walsh functions specified by the Walsh space indicator; and decode the encoded messages received from the base station using the decoder of the data control channel.

Description

Background

Countryside

The present invention relates, in general to communications and, more specifically, to a new and improved method and apparatus for allocating Walsh space in a communications system.

Background

Wireless communication systems are widely used to provide various types of communication, such as voice and data. These systems may be based on multiple code division access (CDMA), time division multiple access (TDMA), or other modulation techniques. A CDMA system provides certain advantages over other types of systems, including increased system capacity.

A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA / EIA-95-B Standard of Base Station to Mobile Station Compatibility for a Broadband Mode Propagation Spectrum Cellular System Dual ”(the IS-95 standard), (2) the standard presented by a consortium called“ Third Generation Partnership Project ”(3GPP) and represented in a series of documents that include Documents No. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (3) the standard presented by a consortium called “Project 2 of the Third Generation Association” (3GPP2) and represented in “subcommittee TR-45.5 , Physical Layer Standard for cdma 2000 ”Spectrum Propagation Systems (the IS-2000 standard), and (4) some other standards.

In the above-mentioned standards, the available spectrum is shared simultaneously between a number of users, and techniques such as soft switching are used to maintain sufficient quality to support delay sensitive services, such as voice. Data services are also available. More recently, systems that increase the capacity for data services have been proposed through the use of higher order modulation, very fast feedback for the Carrier-Interference (C / I) relationship from the mobile station, very fast planning , and planning for services that have more relaxed delay requirements. An example of such a data-only system that uses these techniques is the high transmission rate (HDR) system that meets the TIA / EIA / IS-856 standard (the IS-856 standard).

In contrast to the other standards mentioned above, an IS-856 system uses the entire spectrum available in each cell to transmit data to a single user at a time, selected based on the quality of the link. By doing this, the system uses a higher percentage of time sending data at higher transmission rates when the channel is good, and therefore avoids devoting resources to support transmission at inefficient transmission rates. The effect on the network means greater data capacity, data transmission rates with higher peaks, and a higher average performance.

The systems may incorporate support for delay sensitive data, such as voice channels or data channels supported by the IS-2000 standard, together with support for data packet services such as those described in the IS-856 standard. Such a system is that described in a proposal submitted by LG Electronics, LSI Logic, Lucent Technologies, Nortel Networks, QUALCOMM Incorporated, and Samsung to Project 2 of the Third Generation Partnership (3GPP2). The proposal is detailed in the documents entitled “Updated Proposal for the Shared Physical Layer for 1xEV-DV”, presented to 3GPP2 as document number C5020010611-009, June 11, 2001; “Results of the L3NQS Simulation Study”, presented to 3GPP2 as document number C50-20010820-011, August 20, 2001; and “Results of the Simulation Study for the L3NQS Structure Proposal for cdma2000 1x-EVDV”, presented to 3GPP2 as document number C5020010820-012, August 20, 2001. From now on, these documents will be called proposal 1xEVDV.

A system like the one described in the 1xEV-DV proposal generally includes four-class channels: air channels, IS-95 and IS-2000 dynamic variation channels, a one-way packet data channel (F-PDCH), and some channels backup. Air channel assignments vary slowly, may not change in months. Typically, they are changed when major changes in the network configuration occur. The IS-95 and IS-2000 dynamic variation channels are assigned based on each call or are used for IS95, or IS-2000, Version 0 to B packet services. Typically, the remaining available power of the base station, a Once the air channels and dynamic variation channels have been assigned, it is assigned to the F-PDCH for the remaining data services. The F-PDCH is typically used for data services that are less delay sensitive while IS-2000 channels are used for more delay sensitive services.

The F-PDCH, similar to the traffic channel in the IS-856 standard, is used to send data with the highest data transmission rate to users, one at a time for each cell. On IS-856, when transmitting to a mobile station, all the power of the base station and all the space of Walsh functions are available. However, in the proposed 1xEV-DV system, part of the power of the base station and part of the Walsh functions are assigned to the existing air channels and to the existing IS-95 and cdma2000 services. The rate of data transmission that can be supported depends mainly on the energy and the available Walsh codes once the energy and Walsh codes have been assigned to the air channels, IS-95 and IS2000. Data transmitted through the F-PDCH is propagated using one or more Walsh codes.

In the proposed scheme, the base station only transmits to one mobile station at a time through the F-PDCH, although many users may be using packet services in a cell. The mobile stations are selected for the transmission of the outbound link based on some planning algorithm. One such algorithm is disclosed in US Patent No. 6,335,922, entitled "PROCEDURE AND APPLIANCE FOR THE PLANNING OF THE TRANSMISSION RATE OF THE IDA LINK", granted on January 1, 2002 and assigned to the assignee of this invention.

Due to the discontinuous nature of the data packets, some users' data connections may not be active. These mobile stations enter a state known as an inactive state in many of the CDMA standards (see TIA / EIA / IS-707, Data Service Options for Propagation Spectrum Systems). When the mobile station or base has data to send, a signaling is used to put the mobile station in the traffic channel. From time to time, users can leave or enter the cell, and others can start or terminate their connection. In addition, to receive data on the F-PDCH, each mobile station requires the use of Walsh codes, also called Walsh space, which are also being used for the F-PDCH. Since the Walsh space will tend to vary dynamically over time and may vary between cells (or sectors within a cell), the Walsh space information will need to be relayed to the various users within each cell, including mobile stations that They leave their inactive state. Therefore, there is a need in the art for an allocation of the Walsh space that effectively distributes the Walsh space to the various users while minimizing the use of system resources for distribution.

An article published by Chih-Lin et al., Entitled “Assignment of Charges Based on Interference and Interference for Integrated Services in Wireless Systems of CDMA”, discloses a procedure to provide a regular migration route to the service of data traffic discontinuous with transmission rates of up to four to eight times the basic channel transmission rate in standard CDMA wireless networks.

Another report published by Chih-Lin and others, entitled “Performance of Multicore Wireless Personal Communication Networks,” discloses a multi-code CDMA technique to provide a service of variable transmission rates with different quality requirements by varying the number of codes assigned to the user.

PCT Publication No. WO 99/45669 discloses an apparatus for incorporating multiple data transmission rates into a multiple access communications system with direct orthogonal sequence code division.

PCT Publication No. WO 00/24157 refers to a channel allocation device and a procedure in a CDMA communications system. The document discloses the transmission of a Walsh code index to a mobile station. The document also discloses the encoding of messages and the transmission of the encoded messages to the mobile station.

Summary

The present invention relates to methods and an apparatus as defined in the appended claims.

The embodiments described herein encompass the need for a Walsh space allocation that effectively distributes the Walsh space to the various users while minimizing the use of system resources for distribution. In one aspect, a list of Walsh functions is maintained at the base station and mobile stations. A Walsh space indicator is transmitted to indicate which of the Walsh functions in the list will be used in the communication. The Walsh space indicator is updated according to the dynamic variation transmission power available, or with the use of Walsh functions within the base station. Procedures are provided by which a mobile station may request information about the Walsh space. In another aspect, a Walsh space indicator is continuously emitted for mobile stations to detect the Walsh space indicator. In yet another aspect, the Walsh space indicator is used to initialize convolutional encoders and decoders, to provide a mechanism to mitigate the errors introduced while receiving the Walsh space indicators.

Other diverse aspects are also presented.

The invention provides methods and system elements that implement various aspects, embodiments, and features of the invention, as described below in greater detail.

Brief description of the drawings

The characteristics, nature, and advantages of the present invention will be more apparent from the detailed description set forth below and taken together with the drawings, in which the same reference characters identify correspondingly in all of them, and in the which:

FIG. 1 is a wireless communication system that supports a number of users, and that can implement various aspects of the invention;

FIG. 2 represents an exemplary base station;

FIG. 3 represents an exemplary mobile station;

FIG. 4 is a flowchart representing an embodiment of a procedure for transmitting a Walsh space indicator;

FIG. 5 is a flow chart of an embodiment of a method for optionally including a Walsh space indicator in another message package;

FIG. 6 represents a procedure whereby a mobile station can transmit the need for information from the Walsh space to a base station;

FIG. 7 represents an alternative procedure whereby a mobile station can transmit the need for information from the Walsh space to a base station;

FIG. 8 represents another alternative procedure whereby a mobile station can transmit the need for information from the Walsh space to a base station;

FIG. 9 shows the temporal relationship between a transmission of WALSH_PACE through the F-WICH (Ida's Walsh Information Channel) and the use of said WALSH_SPACE through the F-PDCH;

FIG. 10 is a flow chart of an embodiment of a procedure for receiving the F-WICH;

FIG. 11 is a flow chart of an embodiment of a procedure for receiving the F-WICH and using the initialization of a convolutional decoder as an interlocking mode to mitigate the errors received through the F-WICH; Y

FIG. 12 is a flowchart depicting an embodiment of a procedure for transmitting the Walsh space information during switching.

Detailed description

FIG. 1 is a diagram of a wireless communication system 100 that supports a number of users, and that can implement various aspects of the invention. System 100 may be designed to support one

or more CDMA standards and / or designs (e.g., the W-CDMA standard, the IS-95 standard, the IS-2000 standard, the IS-586 standard, the 1xEV-DV proposal). For simplicity, the system 100 is shown with three base stations 104 in communication with two mobile stations 106. The base station and its coverage area are often collectively referred to as "cell." In IS-95 systems, a cell can include one or more sectors. In the W-CDMA specification, each sector of a base station and the coverage area of the sector is called a cell. As used herein, the term base station may be used interchangeably with the term access point. The term mobile station may be used interchangeably with the terms user equipment (UE), subscriber unit, subscriber station, access terminal, remote terminal, or other corresponding terms in the art. The term mobile station covers fixed wireless applications.

Depending on the CDMA system implemented, each mobile station 106 can communicate with a base station 104 (or possibly more) through the one-way link at any given time, and can communicate with one or more base stations through the reverse link depending on whether The mobile station is in a regular switching or not. The forward link (i.e. the downlink) refers to the transmission from the base station to the mobile station, and the reverse link (i.e. the uplink) refers to the transmission from the mobile station to the station base.

For clarity, the examples used in describing this invention may assume the base stations as originators of the signals and the mobile stations as receivers and the acquirers of said signals, that is the signals through the forward link. Those skilled in the art will understand that mobile stations, as well as base stations, may be equipped to transmit data as described herein and that aspects of the present invention are also applicable in such situations. In this document, the word "exemplary" has the sole meaning of "serving as an example, case, or illustration". Any embodiment described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other embodiments.

A common application for communication system 100 is to provide a packet data service, including an Internet connection. A base station 104 may comprise one or more base station transceiver subsystems (BTS), connected to a base station controller (BSC). A Data Packet Service Node (PDSN), used to send data to a network, such as the Internet, and receive it from it, connects to the BSC within one or more base stations to provide packet services to mobile stations in communication with it through one or more BTS. Various protocols for data packets are known in the art and can be applied at appropriate locations through communication system 100. These details are not shown in FIG. one.

As described above, a system like the one described in the 1xEV-DV proposal uses the remaining transmission energy, once the energy has been allocated to support existing channels such as voice, to transmit with the highest rate of Supportable transmission to a single mobile station at the same time. A 1xEV-DV system can also transmit to multiple mobile stations at the same time, a mode that is also supported within the scope of the present invention. The data channel for one-way transmission is called the One-packet Data Channel (F-PDCH). The choice of the mobile station for transmission is based largely on the channel quality indicators, which are transmitted to the base station by each mobile station with a packet data connection. The channel quality indicator messages are sent to the base station through a channel called Reverse Channel Quality Indicator Channel (R-CQICH). The base station will avoid sending to a mobile station that is currently experiencing low channel quality, instead opting to send another mobile station at a high transmission rate, returning to the first once the channel quality improves .

The base station uses one or more control channels in association with the outbound data channel. One such channel is the Primary One-Way Data Packet Control Channel (F-PPDCCH), another is the Secondary One-Way Data Package Control Channel (F-SPDCCH). The control channels can be used to transmit broadcast information to all mobiles, or messages pointed to a single mobile. A control message can indicate which mobile phone should receive the data through the F-PDCH, the transmission rate, the number of packets, and similar information.

A sending and retransmission protocol can be established to ensure that packets destined for mobile stations arrive when they are transmitted. A mobile station sends an acknowledgment to the base station when it receives a packet through the outbound data channel. This acknowledgment can be sent through the Reverse Recognition Channel (R-ACKCH). If the arrival of an acknowledgment from a mobile station fails once the base station has transmitted to it, the base station may retransmit the packet. In the exemplary embodiment, the base station will attempt to retransmit a packet four times.

Mobile stations can also transmit data to the base station through the reverse link. A channel for the transmission of reverse link data is called the Supplementary Inverse Channel (R-SCH). To indicate the rate of data transmission transmitted through the R-SCH, a reverse link control channel called the Reverse Transmission Rate Indicator Channel (R-RICH) is used.

Data transmitted through the outbound data channel, or F-PDCH, can be dispersed using one or more Walsh codes. In this exemplary embodiment, the data can be covered using up to 28 Walsh codes. As described above, the amount of transmission power available for the F-PDCH transmission, and the number of Walsh channels required, vary as the amount of voice channels and other data channels varies. It is necessary for the base station to be able to communicate to the mobile stations the amount of Walsh channels that are being used during the upstream transmissions, what Walsh channels they are, and the order that the data will be modulated through the Walsh channels. This collective set of information can be called the Walsh space.

FIG. 2 represents an exemplary base station 104. For clarity, only a subset of the components related to this description is shown. The forward link signals are transmitted from an antenna 210, and the reverse link signals are received by it. The forward link signals are generated in a transmitter 250, shown communicatively coupled to an encoder 260. The transmitter 250 can process the data for transmission using a variety of methods, known in the art. Some examples of such processing include Walsh coverage, pseudo-random noise dispersion (PN), interlacing, coding, radio frequency processing (RF) such as up conversion and carrier modulation, and the like. When transmitting data through the F-PDCH, the transmitter 250 covers the appropriate data symbols with the corresponding Walsh functions as defined in the Walsh space at that time. Encoder 260 may be included as part of transmitter 250, but in FIG. 2 is shown as a separate element for clarity of the subsequent analysis. Elcoder 260 may employ various coding schemes, some examples being Cyclic Redundancy Check (CRC) coding, convolutional or block coding, turbo coding, and the like. Among other data that can be transmitted through the forward link via transmitter 250 and antenna 210, for example data packets, as described with respect to FIG. 1, are the messages generated in the generator of messages 240. The messages generated in message generator 240 may be control messages for transmission through the F-PPDCH or FSPDCCH, which are processed and transmitted in transmitter 250.

The reverse link signals are sent from the antenna 210 to the receiver 220, where various processing methods, known in the art, are used to retrieve data from the reverse link signals. Some examples of processing that can be performed on receiver 220 include amplification, downward RF conversion, demodulation (including PN scatter suppression and Walsh decovering), combination, deinterlacing, decoding, and the like.

The passing data of the receiver 220 may have various destinations, one of which is shown as the message decoder 230. The message decoder 230 can decode various messages sent from one or more mobile stations, such as the reverse link messages described above. . The message generator 240 is sensitive to the message decoder 230, in the sense that some reverse link messages are generated in response to the information carried in the reverse link messages. Some examples of this will be detailed in various embodiments below. Note that a typical base station may include a central processing unit (CPU) or a digital signal processor (DSP) to interconnect and manage the various functional blocks described (the CPU or DSP is not shown). In fact, the various blocks of FIG. 2, including message generator 240 and message decoder 230, can be processes that run on a CPU or a DSP. The functional blocks shown are only for clarity of analysis, since those skilled in the art will recognize the multitude of ways to implement the blocks described here in special purpose hardware, be it a CPU or a DSP, or combinations thereof, all of this. within the scope of the present invention. The communication link between message decoder 230 and message generator 240 may include various blocks that are not shown, such as the CPU or DSP mentioned above.

FIG. 3 represents an exemplary mobile station 106. For clarity, only a subset of the components related to this description is shown. The reverse link signals are transmitted from an antenna 310, and the forward link signals are received by it. The reverse link signals are generated in a transmitter 350. The transmitter 350 can process the data for transmission using a variety of methods, known in the art. Some examples of such processing include Walsh coverage, pseudo-random noise dispersion (PN), interlacing, coding, radio frequency processing (RF) such as up conversion and carrier modulation, and the like. Among other data that can be transmitted through the reverse link by means of the transmitter 350 and the antenna 310 are the messages generated in the message generator 340. The messages generated in the message generator 340 may be control messages such as quality of the channel, recognition, transmission rate information and the like. Some examples include R-CQICH, R-ACKCH, and R-RICH, each of which is processed and transmitted in transmitter 350.

The outbound link signals are sent from the antenna 310 to the receiver 320, where various processing methods, known in the art, are used to retrieve data from the outbound link signals. Some examples of processing that can be performed at receiver 320 include amplification, downward RF conversion, demodulation (including PN scatter suppression and Walsh decovering), combination, deinterlacing, decoding, and the like. Decoder 360 is communicatively coupled. receiver 320. The decoder 360 may be included as part of the receiver 320, but in FIG. 3 is shown as a separate element for clarity of the subsequent analysis. The decoder 360 can be decoded according to one or more of the various coding schemes known in the art. Some examples include CRC encoders, convolutional encoders, turbo encoders, and the like. Upon receiving data through the F-PDCH, the receiver 320 discovers the appropriate data symbols with the corresponding Walsh functions defined in the Walsh space at that time.

The data of the receiver 320 may have various destinations, one of which is shown as the message decoder 330. The message decoder 330 can decode various messages sent from one or more mobile stations, such as the forward link messages described above. . Message generator 340 is sensitive to message decoder 330, in the sense that some reverse link messages are generated in response to the information carried in the outbound link messages. Some examples

of this will be detailed in various embodiments below. Note that a typical base station can

include a central processing unit (CPU) or a digital signal processor (DSP) to interconnect and

manage the various functional blocks described (the CPU or the DSP are not shown). In fact, the various

5 blocks of FIG. 3, including message generator 340 and message decoder 330, can be

processes that run on a CPU or a DSP. The functional blocks shown are for clarity only

of analysis, since those skilled in the art will recognize the multitude of ways to implement the blocks here

described in special purpose hardware, either a CPU or DSP, or combinations thereof, all

this within the scope of the present invention. The communication link between message decoder 330 and 10 message generator 340 may include various blocks that are not shown, such as the CPU or DSP

previously mentioned.

FIG. 4 represents a flow chart of an embodiment of a procedure for communicating the information of the

Walsh space to mobile stations. A message is sent through the broadcast channel, called Channel

One-Way Emission Control (F-BCCH), which contains the Walsh numbers and the number of channels for 15 different one-way channels, including the F-PPDCCH, the F-SPDCCH, the F-PDCH. In the exemplary embodiment, the F

PDCH can use up to 28 Walsh functions. In this document, the list of functions for use in the

Transmission and reception of the F-PDCH is called the Walsh list. In an alternative embodiment, a

default list instead of using the Walsh list for transmission through the F-BCCH. Table 1 shows

shows an example of a Walsh list. In this example, the Walsh functions to be used are 31, 15, 30, 14, and so on. In addition to the Walsh list, the base station and mobile stations need to agree

with the order in which the symbols are applied to the various functions of Walsh, in order to facilitate a

proper decoding. One solution is to use the order of the Walsh list, although any procedure of

Walsh function selection is within the scope of the present invention. In decision block 410

of FIG. 4 is displayed if a default list is used. Otherwise, it goes to block 420 and list 25 of the Walsh space is issued. If a default modulation order is not specified, such as the order of the list of

Walsh, said modulation order can be specified by issuing the modulation order, also in the block

410.

Table 1

Default Walsh Space for FPDCH (in Space 32)

31

fifteen

30

14

29

13

28

12

27

eleven

26

10

25

9

(keep going)

Default Walsh Space for FPDCH (in Space 32)

24

8

2. 3

7

22

6

twenty-one

5

twenty

4

19

3

18

2

Once the entire Walsh space is defined, the subspace to be used for any particular transmission through the F-PDCH can be indicated by a single number, referred to herein as the indicator for the Walsh space, or WALSH_SPACE. The Walsh space indicator specifies how many Walsh functions are to be used. The Walsh list, and its associated modulation order, can then be used with the Walsh space indicator to identify Walsh functions for use in data communication. An example is shown in Table 2 in which the Walsh subspace corresponding to WALSH_SPACE is equal to six. In this example, six Walsh functions will be used, and will be 31, 15, 30, 14, 29 and 13, in that order. Walsh's space

10 must initially be transmitted to all mobile stations in block 430. When the Walsh space changes, the Walsh space indicator must be sent to identify the new Walsh space. This is shown in block 440 of FIG. 4, where the flow makes a return loop to decision block 440 when the Walsh space has not changed, but goes to block 430 to send the Walsh space indicator when it has changed.

Table 2 Any number of different tables can be supported within the scope of the present invention. Table 3 shows a Walsh space by default, suitable as a Walsh default by default to assign Walsh channels during data transmission through a channel such as the F-PDCH.

Walsh Space Example WALSH_SPACE = 6

31

fifteen

30

14

29

13

Table 3 5

Alternative Walsh Default Space for FPDCH (in space 32)

31

fifteen

2. 3

7

27

eleven

19

3

29

13

twenty-one

5

25

9

30

14

22

6

26

10

18

2

28

12

twenty

4

24

8

10

fifteen

twenty

25

30

35

40

Four. Five

In the exemplary embodiment, the Walsh space indicator is sent in a message, of which an example is shown in Table 4. In this example, the message has 13 bits of information with 6 bits assigned to the multiple access control identifier. (MC-ID), and 7 bits used to signal the package structure. In this exemplary embodiment, a MAC-ID of 0 indicates control, which can be used to broadcast to all mobile stations that are monitoring base station transmissions. Of the remaining 7 bits, two are used to indicate the type of information and the remaining 5 bits indicate the number of Walsh functions that are being used. In this example, CON_INFO_TYPE can be used to indicate that the message contains a Walsh space indicator . The WALSH_SPACE is a 5-bit number that indicates the number of Walsh functions that are being used. The message can be sent through a control channel. In the exemplary embodiment, the Walsh Space Indicator message can be sent through the F-SPDCCH.

Table 4

Countryside

Length (bits) Value

MAC_ID

6 000000

CON_INFO_TYPE

2

WALS_ SPACE H

5

In the proposed 1 xEV-DV, messages through the control channel, such as the F-SPDCCH, can be transmitted using packets of 1, 2, or 4 slots. When the 8-slot format is used for the F-PDCH, a 4-slot format is used for the F-SPDCCH. If F-PDCH transmissions with 8 slots are not being used, it may be necessary to send a Walsh Space Indicator message through the F-SPDCCH, using part of the one-way link capability.

In FIG. 5 shows a flow chart representing an embodiment of this procedure. The flow effects a return loop from decision block 510 to itself when a Walsh update is not required. When a Walsh update is required, it is passed to decision block 510, to determine if a time is elapsing in which the F-PDCH is being transmitted but a control message is not being transmitted. If so, it is passed to block 530 and the Walsh Space Indicator message is transmitted using the reservation control message. Otherwise, block 540 is passed and the Walsh Space Indicator message is transmitted using the dedicated control message.

One of the situations in which the percentage of 8-slot packets is low occurs when the channel is being used for data-only operations (of the 28 Walsh codes, all are available). In this situation, a change in the Walsh space may require a special transmission of the Walsh Space Indicator message through the control channel, reducing the total system capacity. However, in situations like this, Walsh's space is not changing dramatically, so that the effect on the entire system capacity is minimal.

The Walsh space may change more dynamically when one of the channels is assigned to the voice or other services other than the F-PDCH services. In this case, a larger fraction of the 8-slot transmissions will be available since the amount of available energy is less.

In general, each time the base station changes the Walsh space, the Walsh space indicator should be transmitted. In the exemplary embodiment, the Walsh space information can be sent to the mobile station during call preparation using the Extended Channel Assignment Message (ECAM), defined in the IS2000 standard. If the Walsh space changes subsequently, the base station can update the mobile station using the F-SPDCCH message with the Walsh Space Indicator.

Additionally, there may be circumstances in which the mobile station may want to communicate a need for information from the Walsh space to the base station. For example, a mobile station may need to be updated with the Walsh space information when switching or requesting that F-PDCH transmissions occur from a new cell or sector. There are a variety of techniques that the mobile station can use to communicate this to the base station.

In one embodiment, represented in FIG. 6, the mobile needs information from the Walsh space, as shown in step 610. The mobile communicates this to the base station by not transmitting the inverse quality indicator, for example the R-CQICH. If the base station does not receive the R-CQICH, then it does not transmit data to the mobile station, but instead can transmit the information from the Walsh space. In an alternative embodiment, shown in FIG. 7, the mobile responds to the need for Walsh space information, step 710, by sending a special value through the R-CQICH, one that is not used for regular operation, for example. This last provision is useful when transmissions from the mobile station are sometimes not received.

5 Any of these procedures can be used to activate the sending of Walsh space information at the base station via the outbound link. Using the alternative procedure, shown in FIG. 7, the special value through the R-CQICH can be used to facilitate the update of Walsh space information during a broadcast or when a cell or sector already present in the active group is requested to transmit to the mobile station. The R-CQICH contains information on the relationship between Carrier and Interference (C / I) corresponding to a specific base station. A mobile station, subsequent to the broadcast, can send this special value with indication of the new base station, and the base station knows that it needs to send the Walsh space information. A system that uses Walsh coverage of C / I messages to direct messages to a particular base station is disclosed in US Patent Application, codependent, Serial No. 08 / 963,386, entitled "PROCEDURE AND APPLIANCE FOR PACK TRANSMISSION OF DATA WITH HIGHER TRANSMISSION RATE ”, presented on 3

November 15, 1997, and assigned to the assignee of the present invention.

FIG. 8 represents another method for communicating a need for information on the Walsh space, shown in step 810. In step 820, the mobile sends a channel quality indicator, through the R-CQICH, for example, in a normal manner. In step 830, a special value is sent through one of the other reverse control channels. For example, through a transmission rate indicator channel, such as R-RICH, a value that is not otherwise used can be used to indicate a valid transmission rate. Alternatively, a special value can be sent through a recognition channel, such as R-ACKCH. Another way would be to have a special channel exclusively for this function. When using another channel, the base station obtains information on the channel quality indicator from the mobile station, and therefore allows the base station to use the quality indicator information to select a time to transmit the Walsh space information When the channel is good. This

25 increases the chances that the mobile station properly receives the information, reduces the amount of energy to transmit the information from the Walsh space, or both.

To determine the probability of error for receiving information from the Walsh space when feedback of the channel quality from the mobile station is not used, long-term attenuation statistics can be used. As an example, for a 1% one-way error (FER) transmission rate, the control channel requires in the worst case 18 dB Eb / Nt (energy per bit / thermal noise), at approximately 30 km / hr in a fading environment of Rayleigh with 1 route. The Ec / Ior formula (energy per chip / total energy transmitted from the base station) is given by:



⎛

⎞⎛

⎞



Ec

Eb

R

one

⎜

⎜⎝

⎟⎠⎜⎝

⎟⎠

⎟

Equation 1

=

Ior

Nt

W

G

where R is the data transmission rate, W is the transmission bandwidth, and G is the geometry

35 (relationship between the energy from the cell that the mobile is monitoring and that of all other cells), in dB. A message contains 29 bits, therefore the Ec / Ior required for a 1-slot housing is 0.7 dB - G. It is clear that there is not enough energy for detection near the cell limits (G is 0 dB or less). However, if the Walsh space information is repeated, and a 1% FER is desired after two repetitions (and assuming the fading is independent between repetitions), then the Eb / Nt is about 8 dB and the Ec / Required for a 1-slot housing is -10.3 dB - G. The total energy, in terms of Ec / Ior, is -7.3 - G. Therefore, using a relatively large portion of the channel energy, Walsh space indication can be transmitted reliably to the mobile station. Further on, alternative embodiments are analyzed, which do not require such a large portion of the channel energy for reliable transmission.

An alternative procedure for communicating Walsh space information is to use a channel multiplexed by

45 code division, continuously transmitted. This channel will be referred to herein as the Walsh Ida Channel Indicator Channel, or F-WICH. Using this procedure has the advantages that Walsh space is allowed to be transmitted with low energy. The mobile station can combine power from the repetition of the Walsh space. The temporal diversity introduced by repeating the information can soften the processes that present an excess of fading. Additionally, mobile stations do not need to transmit a need for information from the Walsh space to the base station, since the information is being continuously broadcast.

In the exemplary embodiment, a 20 ms cycle and a Walsh function with a length of

256. There will be 96 symbols available per cycle. A simple block code may be used, such as a code (24, 7) repeated four times, similar to that used for the R-RICH, as defined in the 1xEV-DV proposal.

The base station continuously sends the F-WICH. When the Walsh space changes, the base station transmits the new Walsh space indicator with one cycle, plus several slots (eg 2), in advance with respect to the change in the air itself. In the context of the IS-95 and cdma2000 interfaces, the duration of a slot is the same as that of a power control group, the length of both being 1.25 ms. FIG. 9 shows this relative timing. WALSH_SPACE is transmitted through the F-WICH. After 20 ms plus a certain number of slots (eg, two), the 16 slots corresponding to the updated WALSH_SPACE are transmitted through the F-PDCH.

The mobile station decodes the F-WICH at each cycle. If the F-WICH is not received correctly, there are a variety of strategies that the mobile station can use. One is to assume the previous value of the WALSH_SPACE, which is useful if the WALSH_SPACE does not change too often. A second strategy is simply to wait for the new F-WICH transmission. The mobile station may use other techniques, such as those described above in relation to FIGS. 6-8, to inform the base station. Although, as mentioned above, it is not necessary for the base station to know that the mobile station has not received the Walsh information correctly, since the information is being transmitted continuously, there are other considerations that can make such communication be useful

For example, in the proposed 1xEV-DV, a retransmission scheme is used so that each packet can be delivered to a mobile station up to four times, waiting for a packet recognition. If the mobile station does not have the correct Walsh space, then it is most likely that all four transmissions present a transmission error (even if the channel was good during the transmission). An upper layer retransmission protocol (eg, RLP) will handle this situation correctly, but the system's resources and capacity are wasted when transmitting to a mobile station unable to receive. This is why it may be desirable for a base station to receive an indication from a mobile station that it has not received Walsh's space, to avoid transmission until the mobile station can receive again. The mobile station can communicate this by not transmitting the channel quality indicator, such that the R-CQICH, as shown in FIG. 6. Or a special value of the channel quality indicator can be transmitted, as shown in FIG. 7. Other reverse alternative channels may also be used to indicate the lack of a valid Walsh space decoding by the mobile station, such as the reverse transmission rate indicator, or R-RICH, or the recognition channel, or R -ACKCH.

If the mobile station does not correctly receive the Walsh space indicator through the F-WICH in one cycle, you can combine the system symbols that were received in the previous cycle with those of the current cycle. This provides an additional 3 dB of energy to decode the Walsh space indicator. However, if the Walsh space indicator has changed from one transmission to the next, then there is a high possibility that the transmission has not been decoded. Therefore, this type of approach is likely to be used when the Walsh space indicator does not change very often.

In FIG. 10 shows a flow chart representing an exemplary embodiment of a procedure for sending and receiving the F-WICH. Block 1010 indicates that the base station continuously transmits the F-WICH. It goes to block 1020, where the mobile station receives the next F-WICH cycle. It is passed to decision block 1030. If, in decision block 1030, the F-WICH has been decoded correctly, it is passed to block 1040 to transmit the reverse channel quality indicator, through the R-CQICH, for example . It goes back to block 1020 to receive the next cycle.

If, in decision block 1030, the F-WICH has not been decoded correctly, it is passed to block 1050, and the cycle symbols are combined with the symbols of the previous cycle. It is passed to decision block 1060. In decision block 1060, if the F-WICH has been correctly decoded from the combined symbols, it is passed to block 1040 and the reverse channel quality indicator is transmitted, as described above. . If the combined symbols are not decoded correctly, it is passed to block 1020 to receive the next cycle, as described above, or passed to optional block 1070 (represented by a broken line), to notify the base station that the F -WICH was not received correctly. Previously, various notification procedures to the base station have been described, including not transmitting the reverse channel quality indicator, sending a special channel quality indicator value, sending a special value through another reverse channel, and the like. From block 1070, you go to block 1020 to receive the next cycle. Table 6 highlights the various possible outcomes, using slightly different decision rules, using decoding results for two sequential cycles, labeled i-1 and i.

An alternative embodiment can be used, using a different code division multiplexing channel, such as the F-WICH, to mitigate the problems associated with the incorrect reception of a WALSH_SPACE value by a mobile station through the F-WICH. In one embodiment, a cyclic redundancy check (CRC) encoder is initialized, and the base station and the mobile station are initialized using the current value of the WALSH_SPACE. For example, the encoder 260 at the base station and the decoder 360 at the mobile station can be used to calculate the appropriate CRC. If the mobile station has not correctly updated its version of the WALSH_SPACE when the base station has changed it, it is very unlikely that the block header will be properly decoded through the F-SPDCCH. As a result, the mobile station will not receive the subpackage

5

10

fifteen

twenty

25

30

35

40

of that transmission. A possible alternative is to initialize the initial state of the error-correcting encoder (e.g., a convolutional encoder) at the base station (260) and the mobile station (360) using the current value of the WALSH_SPACE. It should be understood that other rules described herein (such as those presented in FIG 10 or Table 6) can also be used, with this alternative embodiment.

Table 6

Result for the i-1 cycle

Result for cycle i Action to take

Good

Good

Use the WALSH_SPACE of cycle i.

Bad

Good Use the WALSH_SPACE of cycle i.

Good

Bad Use the WALSH_SPACE of the i-1 cycle (note that it is likely that the F-SPDCCH header is not decoded correctly if the WALSH_SPACE has changed).

Bad

Bad

Combine the energy of both the i-1 cycle and the i cycle. If it is decoded correctly, then the WALSH_SPACE of the combined cycles is used. If not, the last available WALSH_SPACE is used. Again, it is likely that the F-SPDCCH header is not decoded correctly if the WALSH_SPACE has changed

As before, if the mobile station does not have the correct WALSH_SPACE indication, perhaps due to switching, or errors received in an update through the F-WICH, the mobile station can alert the base station using any of the techniques , such as those mentioned above in relation to FIGS. 6-8. Then, the base station can avoid sending data to that mobile station until it has correctly received the WALSH_SPACE. This avoids wasting system resources by transmitting data to a mobile station that is unable to receive them correctly.

FIG. 11 represents a flow chart of an embodiment of the procedure just described. The mobile station receives cycle i in block 1110. It is passed to decision block 1115 to determine if cycle i has decoded correctly. If so, the WALSH_SPACE included in cycle i is used. The decoder is initialized with the WALSH_SPACE in block 1160, the data control channel is decoded in block 1165, i is increased in block 1170, the next cycle i is received in block 1110, and the process.

If block i has not been decoded correctly in decision block 1115, it is passed to decision block 1125 to determine if the previous cycle, i-1, was decoded correctly. If so, go to block 1155 or use the WALSH_SPACE of the previous cycle. There is no need to combine the cycles, because if the WALSH_SPACE has not changed, the value of the previous WALSH_SPACE is valid, and if it has changed, combining the two different values will probably result in an error anyway. If the Walsh space has changed, then it is very likely that the control channel cannot be decoded since the decoder initialization is not current. The decoder is initialized with the WALSH_SPACE in block 1160, the data control channel is decoded in block 1165, i is increased in block 1170, the next cycle i is received in block 1110, and the process.

If, in decision block 1125, the previous cycle, i-1, was not decoded correctly, it is passed to block 1130 to combine the symbols of both cycles. The decision block 1135 is passed to determine if the combined cycle has been decoded correctly. If so, the WALSH_SPACE of the combined cycles is used. The decoder is initialized with the WALSH_SPACE in block 1160, the data control channel is decoded in block 1165, i is increased in block 1170, the next cycle i is received in block 1110, and the process.

If, in decision block 1135, the combined cycle was not decoded correctly, then it goes to block 1145. The previously available WALSH_SPACE is used. If the Walsh space has not changed, then this value will be valid. If it has changed, then, as before, the control channel will not be properly decoded using this value of the WALSH_SPACE as initialization of the decoder. The decoder is initialized with the WALSH_SPACE in block 1160, the data control channel is decoded in block 1165, i is increased in block 1170, the next cycle i is received in block 1110, and the process. Alternatively, as shown in the optional block 1150 between blocks 1145 and 1160 (represented by broken lines), the mobile station may notify the base station that the F-WICH has not been received correctly, using any of the procedures described above. . It should be understood that in alternative embodiments, block 1150 could notify the base station that the F-WICH was not received correctly at any time when the mobile station did not correctly receive the F-WICH.

Normally, a high reliability channel would require a large amount of transmission energy, particularly in a slow fading environment. However, the energy required for a continuously transmitted F-WICH is lower. This is because the WALSH_SPACE is repeated, thus providing an effective deinterlacing, in the exemplary embodiment, of 40 ms. Additionally, if the mobile station is faded, then the ratio between Carrier Interference (C / I) is low and the base station will not transmit to the mobile station through the data packet channel, such as the F-PDCH. Therefore, there is no need for the mobile station to have the correct Walsh space information. Correct Walsh space information is only required when the channel improves, so that the base station can select that mobile station for transmission.

In an exemplary embodiment, an Eb / Nt of about 4 dB may be suitable for this channel. Since the transmission rate is quite low, the required Ec / Ior can be about -33 dB. To support suchEc / Ior, very little reverse link capacity is needed.

The various embodiments of the present invention, some of which are described above, can also be applied to switching situations. Prior to switching, a base station can send various messages to the mobile station. The NGHBR_CONFIG field of the Universal Neighbors List Message (UNLM) or other Neighbors List Message indicates whether the F-PPDCCH and F-SPDCCH are present and if their Walsh assignments are the same as those of the current base station. For example, if the NGHBR_CONFIG field is equal to ‘000’, then they are the same. Instead of reusing the NGHBR_CONFIG fields of the UNLM, a new field, NGHBR_CONFIG_PDCH can be created to transmit the information. In this case, a single bit could indicate whether the FPPDCCH and the F-SPDCCH are present and their Walsh assignments are the same as those of the current base station.

When a mobile station receives a switching message from a base station, the base station typically sends a Universal Extended List List (EUNLM) Message immediately after switching. In this message, the base station may include the following information: if the F-PPDCCH and the F-SPDCCH are present, the Walsh assignments of the F-PPDCCH and the F-SPDCCH, and the Walsh list of the F-PDCH. Note that a single bit can be used to represent the first two articles. Two more bits can be used; the first to indicate if the Walsh list of the F-PDCH is used by default, the second to indicate whether the Walsh list of the existing F-PDCH can be used (if it is different from the default one). If the default Walsh list is not used, or the existing one, then the base station must send the Walsh list of the F-PDCH to the mobile station. As an alternative to the Universal Extended List List of Neighbors, the base station may send this information in a switching message, such as the Switching Address Message.

FIG. 12 represents a flow chart of an embodiment of this switching procedure. In block 1210, the base station directs the mobile station to switching. In block 1220, the base station sends a message indicating whether the default or existing Walsh list can be used. Go to decision block 1230 to determine if any of the lists can be used. If so, it goes to block 1250 and goes through switching, using the valid list. Otherwise, it goes to block 1240 and sends an updated Walsh list to be used by the mobile station. Then it goes through the switching in block 1250.

It should be noted that in all the embodiments described above, the process steps can be exchanged without departing from the scope of the invention.

Those skilled in the art will understand that information and signals can be represented using any of several technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced through the above description can be represented by voltages, currents, electromagnetic waves, fields or magnetic particles, fields or optical particles, or any combination thereof.

Those skilled in the art will further appreciate that the various and illustrative logic blocks, modules, circuits, and algorithm steps, described in connection with the embodiments described herein, can be implemented as electronic hardware, computer software, or combinations of the same. To clearly illustrate this interchangeability of hardware and software, in what precedes various components, blocks, modules, circuits, and illustrative steps have generally been described in terms of their functionality. Whether such functionality is implemented as hardware or as software depends on the particular application and the design restrictions imposed on the entire system. Those skilled in the art can implement the described functionality in various ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention.

The various blocks, modules, and illustrative circuits, described in connection with the embodiments described herein, can be implemented or executed with a general purpose processor, a digital signal processor (DSP), an integrated circuit for specific applications ( ASIC), an array of field programmable gates (FPGA) or other programmable logic device, discrete gate or logical transistor, discrete hardware components, or a combination thereof designed to perform the functions described in the

5 present document. A general purpose processor may be a microprocessor, but in an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computer devices, e.g. eg, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other similar configuration.

The steps of a procedure or algorithm described in connection with the embodiments described herein can be performed directly on a hardware, in a software module executed by a processor, or a combination of the two. A software module may reside in a RAM, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, portable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the

15 processor so that the processor can read information from the storage medium, and can write to it. In an alternative, the storage medium can be integral with the processor. The processor and storage medium may reside in an ASIC. The ASIC can reside in a user terminal. In an alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The foregoing description of the described embodiments has been provided to allow any person skilled in the art to manufacture or make use of the present invention.

Claims (9)

1.-A procedure for allocating Walsh space in a communications system, comprising: receiving (1020) in a mobile station, from a base station, a Walsh space indicator through a Walsh space indicator channel, in which the Walsh space indicator channel is a multiplexed channel of division of code, transmitted continuously, to communicate a Walsh space indicator, the Walsh space indicator specifying a number of Walsh functions from a list of programmed Walsh functions; receive, on the mobile station, from the base station, coded messages, in which the messages are coded using an encoder at the base station, initialized with the Walsh functions specified by the Walsh space indicator; Y decode the encoded messages received from the base station using the decoder of the data control channel. 2. The method of Claim 1, further comprising sending a signal (1040) to the base station with a detection recognition of the Walsh space indicator. 3. The method of Claim 2, further comprising suppressing the transmission of data packets from the base station in response to a negative detection recognition of the Walsh space indicator. 4. The method of Claim 1, wherein the first decoding stage comprises a first Walsh space indicator channel cycle. 5. The method of Claim 4, wherein the decoding step further comprises: combine (1050) a second cycle of the Walsh space indicator channel with the first cycle of the Walsh space indicator channel when the Walsh space has not been detected; Y decode the combined cycles of the Walsh space indicator channel to detect a Walsh space indicator. 6. The method of Claim 2, wherein the step of sending signals comprises transmitting (1040) a channel quality indicator when the Walsh space indicator is detected. 7. A method as claimed in Claim 1, further comprising: transmit (430), from the base station, the Walsh space indicator to the mobile station through the Walsh space indicator channel; initialize an encoder on the base station with the Walsh functions specified by the encoding messages of the Walsh space indicator, using the encoder; Y transmit the encoded messages from the base station to the mobile station. 8. The method of Claim 7, wherein the coding is a convolutional coding. 9. The method of Claim 7, wherein the coding is a turbo coding.