Source: http://www.google.com/patents/US7555069?dq=5,779,924
Timestamp: 2015-02-28 23:40:05
Document Index: 162183757

Matched Legal Cases: ['art 110', 'art 110', 'art 110', 'art 110', 'art 110', 'art 110']

Patent US7555069 - Apparatus and method for receiving a forward packet data control channel in ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA forward packet data control channel (F-PDCCH) receiver for reducing alarms relating to errors in a packet data control channel for transmitting a control signal in a mobile communication system and a method of using the same. In the F-PDCCH receiver, a decoding part decodes received symbols and calculates...http://www.google.com/patents/US7555069?utm_source=gb-gplus-sharePatent US7555069 - Apparatus and method for receiving a forward packet data control channel in a mobile communication system supporting packet data serviceAdvanced Patent SearchPublication numberUS7555069 B2Publication typeGrantApplication numberUS 10/954,306Publication dateJun 30, 2009Filing dateOct 1, 2004Priority dateOct 2, 2003Fee statusPaidAlso published asCN1799209A, EP1668800A1, US20050138531, WO2005032015A1Publication number10954306, 954306, US 7555069 B2, US 7555069B2, US-B2-7555069, US7555069 B2, US7555069B2InventorsMin-goo KimOriginal AssigneeSamsung Electronics Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (18), Referenced by (2), Classifications (20), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetApparatus and method for receiving a forward packet data control channel in a mobile communication system supporting packet data service
This application claims the benefit under 35 U.S.C. � 119 of an application entitled �Apparatus and Method for Receiving Forward Packet Data Control Channel in a Mobile Communication System Supporting Packet Data Service� filed in the Korean Intellectual Property Office on Oct. 2, 2003 and assigned Serial No. 2003-68951, the entire contents of which are incorporated herein by reference.
The F-PDCCH is a physical channel for carrying a control message that the base station 10 should transmit when there are packets to be transmitted to the in service mobile stations 21, 22 and 23. The F-PDCCH is transmitted the same time as that of F-PDCH for carrying a transmission packet. That is, in order to transmit high-speed packet data, the base station 10 should transmit F-PDCCH together with the F-PDCH. The F-PDCCH has 3 types of slot formats: 1.25 msec (1 slot), 2.5 msec (2 slots), and 5.0 msec (4 slots). The slot formats are selected by a scheduler of the base station 10 every transmission by combining channel information (including a carrier-to-noise ratio (CNR) and a carrier-to-interference ratio (CIR)) and a state of a buffer where transmission data is stored. Herein, the base station 10 does not transmit slot format information (SFI) of the F-PDCCH, determined by the base station 10, to the in service mobile stations 21, 22 and 23. Therefore, the F-PDCCH receivers of the mobile stations 21, 22 and 23 must detect slot format information determined by the base station 10 from a received F-PDCCH signal. Such a slot format detection scheme for a mobile station is called �Blind Slot Format Detection (BSFD).�
The MAC_ID combiner 32 receives 8-bit MAC_IDs for identifying users. In the MAC_ID combiner 32, an 8-bit CRC covered with a MAC_ID is called an �inner frame quality indicator,� and another 8-bit CRC is called an �outer frame quality indicator.� The outer frame quality indicator is exclusive-ORed (or XORed) with an 8-bit binary pattern called a MAC_ID before being transmitted. The reason for XORing a control message with a MAC_ID in the MAC_ID combiner 32 is because double CRCs are used. Therefore, the outer frame quality indicator is represented by an �8-bit CRC-covered MAC_ID.� Here, the MAC_ID refers to a unique number used by a base station in identifying a mobile station.
Aside from a control message for F-PDCH, a receiver can transmit information for correctly recognizing information on a Walsh cover used by a CDMA transmitter. This information is used to transmit Walsh information used by the base station 10 to a mobile station 21, 22 or 23 connected to the base station 10, and is called a �Walsh mask,� and 13-bit information is used for the Walsh mask. If 8 MAC_ID bits are all �0�, the base station 10 transmits Walsh mask information used for a 13-bit information word of F-PDCCH. However, if 8 MAC_ID bits are not all �0�, the base station 10 transmits a control message (for example, packet size and coding rate) for the F-PDCH transmitted with the 13-bit information word. Therefore, the mobile stations 21, 22 and 23 always check the MAC_ID during the F-PDCCH decoding, and perform different operations according to whether the 8 MAC_ID bits are all �0� as a result of the check.
As illustrated in FIG. 4A, a base station, or a transmitter, can continuously perform a maximum of 4 HARQ transmissions. For example, whether or not a packet transmitted to a mobile station A is received successfully, the base station can sequentially transmit new packets to a maximum of 3 mobile stations B, C and D for a non-transmission duration until it transmits a next packet to the mobile station A. This is called �N=4 FHARQ,� and this transmission scheme is called �user diversity.� User diversity has been proposed for maximizing the efficiency of channel resources. For example, as illustrated in FIG. 4B, when several mobile stations requesting a packet data service are inactivated, the base station suspends transmission of the F-PDCCH and only noises exist for the non-transmission duration.
As illustrated in FIG. 7, the Viterbi decoding part 110 considers only a zero state because all code words always join together at the zero state on a trellis by zero state termination. The Viterbi decoding part 110 calculates a path metric difference between a survivor path and a competitor path, which join together at a zero state at the last stage of a frame. An absolute value MD_MLS of the calculated path metric difference increases as a signal-to-noise ration (SNR) of a received signal increases. In addition, the ML_MLS decreases as SNR of a received signal decreases. The MD_MLS is also called a �Yamamoto quality difference� in honor of Mr. Yamamoto who submitted a paper disclosing the contents of MD_MLS.
In Equation (1), �A� denotes a constant having a positive value, and is a value for determining a detection rate of a decoder. As a value of �A� is larger, an error detection rate increases but error correction capability decreases. Therefore, the best �A� must be determined according to a system in use. Such a method should be considered in a system using block convolutional codes with a coding rate of 1/b, and a description thereof will be made herein below.
An information word transmitted by a transmitter is defined as I, a length thereof is defined as L, and a code word corresponding thereto is defined as C. In addition, a sequence transmitted by antipodal signaling (0/1 or +m/−m) this code word is defined as X. Here, �m� denotes a size of a transmission symbol. If an additive white Gaussian noise existing in a channel is defined as N, a sequence Y that a receiver receives becomes Y=X+N. The code word and sequences are expressed as Equations (2) to (6) shown below. In Equations (2) to (6), {R} denotes a set of real numbers, and a received signal has all possible real numbers.
The Viterbi decoding part 110 transmits MD_MLS_1, MD_MLS_2 and MD_MLS_4 acquired through path metric calculation to the false alarm reduction function 140. Then the false alarm reduction function 140 compares the MD_MLS_1, MD_MLS_2 and MD_MLS_4 with the predetermined thresholds MDTH1, MDTH2 and MDTH4, and transmits the comparison results ID1, ID2 and ID4 to the false alarm measurer 145. Here, the predetermined thresholds are previously determined through experiments. For convenience, a value of ID1 is set to �1�, if a value of MD_MLS_1 is larger than or equal to MDTH1. Also, the ID2 and ID4 are set in the same way. The thresholds MDTH1, MDTH2 and MDTH4 can be pre-stored in the false alarm reduction function 140 or can be adaptively changed, under the control of an external controller or the system. For convenience, it is assumed herein that the thresholds MDTH1, MDTH2 and MDTH4 are previously stored in the false alarm reduction function 140.
IF (ID1==�0� and ID2==�0� and ID3==�0�) Then VALID_VITERBI_DECODING=�0� (10)
In Equation (10), if a Viterbi decoding value is set to �0� (VALID_VITERBI_DECODING=�0�), it indicates that the current Viterbi decoding result is invalid. Therefore, the Viterbi decoding value signal is a signal indicating whether 13-bit information word or MAC_ID=�0� information word output from the current F-PDCCH is valid. For example, if the Viterbi decoding value is �0�, it indicates that the Viterbi decoding output is defective. However, if the Viterbi decoding value is �1�, it indicates that the Viterbi decoding output is correct. The F-PDCCH receiver outputs a detection result of the BSFD detector 130, detected according to the Viterbi decoding value. That is, the switch 150 selectively outputs the detection result of the BSFD detector 130 according to the Viterbi decoding value, thereby reducing a false alarm rate.
In step 1005, the F-PDCCH receiver receives MD_MLS_1, MD_MLS_2 and MD_MLS_4 from the Viterbi decoding part 110. Thereafter, the F-PDCCH receiver compares the MD_MLS_1, MD_MLS_2 and MD_MLS_4 with the thresholds MDTH1, MDTH2 and MDTH4, and outputs ID1, ID2 and ID4 as the comparison results. Specifically, in step 1006, the F-PDCCH receiver determines whether MD_MLS_1 output from the Viterbi decoding part 110 is smaller than the threshold MDTH1. If MD_MLS_1 is smaller than MDTH1, the F-PDCCH receiver compares MD_MLS_2 with the threshold MDTH2 in step 1007. If MD_MLS_2 is smaller than the threshold MDTH2, the F-PDCCH receiver compares MD_MLS_4 with the threshold MDTH4 in step 1008. If MD_MLS_4 is smaller than the threshold MDTH4, because a difference between different paths compared with a maximum likelihood path, i.e., a survivor path and a competitor path, is small, it is difficult to determine the maximum likelihood path. As a result, it is difficult to correctly decode forward packet data control channels. Therefore, the F-PDCCH receiver sets the Viterbi decoding value to �0� in step 1009, and indicates a F-PDCCH decoding failure in step 1010.
However, if it is determined in steps 1006 to 1008 that MD_MLS_1, MD_MLS_2 and MD_MLS_4 are larger than or equal to the thresholds MDTH1, MDTH2 and MDTH4, because a path metric difference is large, it is possible to determine a maximum likelihood path. As a result, it is possible to correctly decode forward packet data control channels. Therefore, the F-PDCCH receiver sets the Viterbi decoding value to �1� (VALID_VITERBI_DECODING=�1�) in step 1020, and outputs SFI and MAC_ID in step 1021.
In the operation of steps 1006 to 1008, the false alarm reduction function 140 of the F-PDCCH receiver compares MD_MLS_1, MD_MLS_2 and MD_MLS_4 calculated by the Viterbi decoding part 110 with the thresholds MDTH1, MDTH2 and MDTH4, and outputs ID1, ID2 and ID4 for the MD_MLS_1, MD_MLS_2 and MD_MLS_4, respectively. The IDs output from the false alarm reduction function 140 have a value of �0� or �1�. If ID1=�0�, ID2=�0� and ID4=�0�, the false alarm measurer 145 outputs a Viterbi decoding value of �0�, and otherwise, the false alarm measurer 145 outputs a Viterbi decoding value of �1�. However, the decision method proposed for the false alarm measurer 145 can be set differently by a user or a system, and the embodiment of the present invention pre-performs the decision method using the false alarm measurer 134 thereby reducing a false alarm rate of received forward packet data control channels.
As described above, a mobile station selected by a base station fails to correctly receive F-PDCCH transmitted by the base station due to noises or disturbances, and in particular, mistakes the MAC_ID for an all-zero MAC_ID, i.e., Walsh mask update information, due to the F-PDCCH error. Therefore, the false alarm reduction function sets a Viterbi decoding value to �0� and outputs a signal indicating that a Walsh mask update information is invalid, thereby preventing misoperation of the mobile station.
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