The exemplary embodiments of this invention relate generally to wireless digital communications systems and, more specifically, relate to multi-carrier wireless digital communications systems.
The following abbreviations, at least some of which appear in the description below, are defined as follows:
3GPP2 Third Generation Partnership Project
ACK Acknowledgement
ARQ Automatic Repeat Request
BTS Base Transceiver Station
CDM Code Division Multiplex
CDMA Code Division Multiple Access
DL Downlink
DPCH Dedicated Physical Channel
F-DPCH Fractional Dedicated Physical Channel
FL Forward Link
HRPD High Rate Packet Data
MAC Medium Access Control
RLC Radio Link Control
RNC Radio Network Controller
RNTI Radio Network Temporary Identifier
TDM Time Division Multiplexed
UE User Equipment
UL Uplink
UMTS Universal Mobile Telecommunications System C304
UTRA-FDD UMTS Terrestrial Radio Access-Frequency Division Duplex
UTRAN UMTS Terrestrial Radio Access Network
WCDMA Wideband Code Division Multiple Access
A multiple radio frequency (RF) carrier (Multi-Carrier) system has been proposed to enhance code division multiple access system performance in 3GPP2. In general, Multi-Carrier systems have complex forward link (Base station to user equipment) and reverse link (user equipment to base station) deployments. The forward link and reverse link may be symmetrical or asymmetrical, depending on the application requirements for a given deployment.
It is known to multiplex two acknowledgment (ACK) feedback channels in a reverse link. However, in order to support N (N>2) ACK feedback channels, multiple reverse links, as well as multiple reverse link carriers, are required. The reverse carrier link allocation depends on traffic on the reverse link. For asymmetric traffic (for example, File Transfer Protocol (FTP)), the need to provide multiple reverse link carriers that correspond to the required multiple forward link carriers needed to support the forward link traffic is wasteful of the reverse link resource.
Further, carrier reallocation may be fast and adaptive in multi-carrier systems. The dynamic nature of carrier allocation can complicate the provision of the ACK feedback. At the same, the backwards compatibility of the conventional approach with 1× EV-DO is not maintained. The CDMA 2000 1× EV-DO (Evolution Data Optimized) is a packet data system that offers high speed data rates (of up to 2.4 Mbps) on wireless networks, and is designed to deliver several times the capacity of 1× at similar data rates.
A description of the current ACK feedback mechanism in EV-DO revision A can be found in the specification 3GPP C.S0024-A, version 1.0, March 2004, “cdma2000 High Rate Packet Data Air Interface Specification” in FIGS. 14.2.1.3.1-2 and 14.2.1.3.1-6 (pgs. 14-15, 14-19, and in the description in sub-paragraph 14.2.1.3.3.5, “ACK Channel”, at pgs. 14-31 and 14-32).
As is stated in paragraph 14.2.1.3.3.5, the ACK channel is used by an access terminal to inform the access network whether a physical layer packet addressed to the access terminal, and transmitted on the Forward Traffic Channel, has been successfully received. The access terminal transmits an ACK channel bit in response to every Forward Traffic Channel slot that is associated with a detectable preamble directed to the access terminal. The access terminal is specified to transmit at most one redundant positive ACK in response to a Forward Traffic Channel slot that is detected as a continuation of the physical layer packet that has been successfully received. Otherwise, the ACK channel is gated off.
When acknowledging a Single User packet, the ACK channel uses BPSK (bipolar keying) modulation, with a 1 representing positive acknowledgment and a −1 representing negative acknowledgment. When acknowledging a Multi-User packet the ACK channel uses OOK (ON-OFF keying) modulation, with a 1 (ON) representing positive acknowledgment and a 0 (OFF) representing negative acknowledgment. The access terminal transmits a positive acknowledgment on the ACK channel if it successfully receives a packet addressed to it on the Forward Traffic Channel, otherwise it transmits a negative acknowledgment. A Forward Traffic Channel packet is considered to be successfully received if it has a valid FCS.
A prior proposal for the ACK feedback mechanism for multi-carrier DO can be found in C00AIE-20050310-027, 3GPP2 Air Interface Evolution Technical Expert Meeting, Denver Co., Mar. 10-11, 2005. Page 16 of this document shows a diagram, reproduced as
Another prior proposal can be found in C30-20040518-016, “Reverse Link ACK for Multi-Carrier HRPD”, 18 Apr. 2005. This proposal discusses asymmetric operations between forward and reverse links (with more active FL channels than RL channels), where a common configuration is to have multiple FL channels with a single RL channel.
With regard to a proposed Multi-Carrier ACK channel, it is stated that the effectiveness of asymmetric operation depends heavily on the ability of the Base Station (BS) to communicate MAC layer information such as ACK/NAK, DRC, etc. between the multiple FL channels, and characterizes the above-described earlier proposal as suggesting a configuration in which two FL channels communicate directly without higher layer intervention. In effect, while the TDM approach for ACK/NAK and DRC is recommended, it is asserted that the earlier proposal has significant disadvantages when the number of FLs is increased beyond two.
The proposal found in C30-20040518-016 is said to overcome these limitations by adopting a Code Division Multiplex (CDM) approach, which is said to be more appropriate for Multi-Carrier operations for the following reasons.
The proposed CDM approach is said to be backward compatible with 1× DO (considered as a special case of MC HRPD with a single Walsh Index 0), and is said to allow support of more than two FLs with a single RL. This proposal states that while simultaneous support of 15 channels might not be realistic with a single RL, the CDM approach is said to allow uniform power distribution regardless of the number of FLs supported. Further, it is said that even if the number of FLs is limited to two, the CDM approach allows dynamical selection of data sources among the 15 pre-allocated frequency channels and associated ACK/NAK, without additional upper layer signaling.
The HRPD Rev0 transmits ACK/NAK using BPSK over half a slot (1024 chips) using Walsh channel W84 (with 128 repetitions), while the RevA uses W3212 (with 32 repetitions).
In the proposed CDM approach over the existing RACK Walsh channel, to accommodate up to 15 carriers, each of the channels is associated with a length 16 Walsh code, and the number of repetitions is reduced to eight for HRPD-Rev0, and to two for HRPD-RevA.
In addition, the following recommendations were made:
The foregoing and other problems are overcome, and other advantages are realized, in accordance with the exemplary embodiments of these teachings.
In accordance with an exemplary embodiment of the invention, a method includes generating a plurality of ACK channels, spreading each of the plurality of ACK channels with a separate one of a plurality of Walsh cover codes, combining each of the plurality of ACK channels, and applying a Walsh cover code to the combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, a method includes establishing a plurality of ACK channels each corresponding to a separate forward link channel, individually signal mapping and repeating the plurality of ACK channels, spreading each of the plurality of ACK channels with a separate one of a plurality of Walsh cover codes, combining each of the plurality of ACK channels, and applying a Walsh cover code to the combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, a mobile terminal includes a transceiver, a processor coupled to the transceiver, and a memory coupled to the processor for storing a set of instructions, executable by the processor, for establishing a plurality of ACK channels each corresponding to a separate forward link channel, individually signal mapping and repeating the plurality of ACK channels, spreading each of the plurality of ACK channels with a separate one of a plurality of Walsh cover codes, combining each of the plurality of ACK channels, and applying a Walsh cover code to the combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, a program of machine-readable instructions, tangibly embodied on an information bearing medium and executable by a digital data processor, performs actions including individually signal mapping and repeating a plurality of ACK channels, spreading each of the plurality of ACK channels with a separate one of a plurality of Walsh cover codes, combining each of the plurality of ACK channels, and applying a Walsh cover code to the combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, a network element includes a wireless transceiver, a processor coupled to the wireless transceiver, and a memory coupled to the processor for storing a set of instructions, executable by the processor, for establishing a plurality of ACK channels each corresponding to a separate forward link channel, individually signal mapping and repeating the plurality of ACK channels, spreading each of the plurality of ACK channels with a separate one of a plurality of Walsh cover codes, combining each of the plurality of ACK channels, and applying a Walsh cover code to the combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, a device includes an element for individually signal mapping and repeating a plurality of ACK channels, an element for spreading each of said plurality of ACK channels with a separate one of a plurality of Walsh cover codes, an element for combining each of said plurality of ACK channels, and an element for applying a Walsh cover code to said combined plurality of ACK channels.
In accordance with another exemplary embodiment of the invention, an integrated circuit includes an element for individually signal mapping and repeating a plurality of ACK channels, an element for spreading each of said plurality of ACK channels with a separate one of a plurality of Walsh cover codes, an element for combining each of said plurality of ACK channels, and an element for applying a Walsh cover code to said combined plurality of ACK channels.
The foregoing and other aspects of the exemplary embodiments of this invention are made more evident in the following Detailed Description, when read in conjunction with the attached Drawing Figure, wherein:
With reference to
The ACK feedback mechanism for Multi-Carrier DO in accordance with exemplary embodiments of the invention uses a Code Division Multiplex (CDM) approach, wherein a plurality of FL channels can be ACKed, and where each ACK channel is assigned a separate Walsh code that is applied on a per ACK channel basis after ACK signal mapping and sequence repetition. The ACK channels are then combined and spread using a W3212 from a length 32 Walsh code.
In the exemplary embodiment shown, the separate Walsh codes for each ACK channel are selected from a length 16 Walsh code (W160-W1615), the ACK signal mapping is as follows: (ACK=+1, NAK-1, OFF=0), and the sequence repetition is 2×.
As noted, the exemplary embodiment shown in
With reference to
In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
The embodiments of this invention may be implemented by computer software executable by a data processor of the UE 10, or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that the various blocks shown in
With reference to
The ACK feedback mechanism for Multi-Carrier DO in accordance with the exemplary embodiments of the invention provides flexibility for dynamic operation with multiple FL channels, and furthermore is backwards compatible with earlier ACK feedback approaches.
In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
Programs, such as those provided by Synopsys, Inc. of Mountain View, Calif. and Cadence Design, of San Jose, Calif. automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or “fab” for fabrication.
Various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications of the teachings of this invention will still fall within the scope of the non-limiting embodiments of this invention.
Furthermore, some of the features of the various non-limiting embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.
This Application claims the benefit under 35 USC 119(e) of U.S. Provisional Application No. 60/678,436 filed May 6, 2005.
Number | Date | Country | |
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60678436 | May 2005 | US |