# US 8,787,177 B2 · Techniques for radio link problem and recovery detection in a wireless communication system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,177 B2 - Document ID: US8787177B2 - Status: Granted - Kind: B2 - Application number: 12/263,998 - Filed: 2008-11-03 - Published: 2010-05-06 - Granted: 2014-07-22 - Earliest claimed: 2008-11-03 - Assignees: Apple Inc. - Applicants: Ian Wong; Taeyoon Kim - Inventors: Ian Wong; Taeyoon Kim - Web page: https://patentgrep.com/patent/US8787177B2 ## CPC - H04W 24/08: Testing, {supervising or monitoring} using real traffic - G06F 11/076: {by exceeding a count or rate limit, e.g. word- or bit count limit} - G06F 11/0793: {Remedial or corrective actions (recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40)} - H04B 17/336: Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR] - H04J 11/0023: {Interference mitigation or co-ordination (direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541)} - H04L 1/203: {Details of error rate determination, e.g. BER, FER or WER} - H04W 24/00: Supervisory, monitoring or testing arrangements - H04W 24/10: Scheduling measurement reports {; Arrangements for measurement reports} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04B: TRANSMISSION - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A technique for radio link detection in a wireless communication system includes estimating a first error rate of an indicator channel. In this case, the indicator channel includes an indication of a number of symbols in a control channel. A second error rate of the control channel is also estimated. The first and second error rates are then combined to provide a performance metric. Based on the performance metric, a determination is made as to whether a radio link problem exists. ## Claims ### Claim 1 A method for radio link detection in a wireless communication system, comprising: at a subscriber station, estimating a first error rate of an indicator channel, wherein the indicator channel includes an indication of a number of symbols in a control channel; where the estimating of the first error rate is based on one or more reference signals associated with the indicator channel; estimating a second error rate of the control channel; where the estimating of the second error rate is based on one or more reference signals associated with the control channel; combining the first error rate of the indicator channel with the second error rate of the control channel to provide a combined performance metric based on both the indicator channel and the control channel; determining whether a radio link problem exists based on the combined performance metric exceeding a first threshold; and if the radio link problem exists, disabling transmission by the subscriber station. ### Claim 2 (depends on 1) The method of claim 1, further comprising: indicating a radio link failure when the radio link problem persists for a first time period. ### Claim 3 (depends on 1) The method of claim 1, further comprising: indicating a radio link recovery when the combined performance metric is below a second threshold. ### Claim 4 (depends on 1) The method of claim 1, wherein the first and second error rates are block error rates. ### Claim 5 (depends on 1) The method of claim 1, wherein the indicator channel is a physical control format indicator channel. ### Claim 6 (depends on 1) The method of claim 1, wherein the control channel is a physical downlink control channel. ### Claim 7 (depends on 1) The method of claim 1, wherein the first and second error rates are scaled and then added together to provide the combined performance metric. ### Claim 8 (depends on 1) The method of claim 1, wherein the estimating a first error rate of an indicator channel further comprises: estimating a signal-to-interference-and-noise ratio for the indicator channel; and mapping the estimated signal-to-interference-and-noise ratio for the indicator channel to the first error rate, and wherein the estimating a second error rate of the control channel further comprises: estimating a signal-to-interference-and-noise ratio for the control channel; and mapping the estimated signal-to-interference-and-noise ratio for the control channel to the second error rate. ### Claim 9 (depends on 1) The method of claim 1, wherein the first error rate is based on an effective signal-to-interference-and-noise ratio for the indicator channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the indicator channel. ### Claim 10 (depends on 1) The method of claim 1, wherein the second error rate is based on an effective signal-to-interference-and-noise ratio for the control channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the control channel. ### Claim 11 (depends on 1) The method of claim 1, wherein the first and second error rates are averaged over a predetermined time period. ### Claim 12 A wireless communication device, comprising: a transmitter; a receiver; and a processor coupled to the receiver, wherein the processor is configured to: estimate a first error rate of an indicator channel, wherein the indicator channel includes an indication of a number of symbols in a control channel, estimate a second error rate of the control channel; combine the first error rate of the indicator channel with the second error rate of the control channel to provide a combined performance metric based on both the indicator channel and the control channel, where the combined performance metric comprises an estimated combined Block Error Rate (BLER) of the indicator channel and the control channel; and determine whether a radio link problem exists based on the combined performance metric exceeding a first threshold, wherein the processor is further configured to, when the radio link problem exists, power down the transmitter. ### Claim 13 (depends on 12) The wireless communication device of claim 12, wherein the processor is further configured to: indicate a radio link failure when the radio link problem persists for a first time period. ### Claim 14 (depends on 12) The wireless communication device of claim 12, wherein the processor is further configured to: indicate a radio link recovery when the combined performance metric is below a second threshold. ### Claim 15 (depends on 12) The wireless communication device of claim 12, wherein the first and second error rates are block error rates, and wherein the indicator channel is a physical control format indicator channel and the control channel is a physical downlink control channel. ### Claim 16 (depends on 12) The wireless communication device of claim 12, wherein the first error rate is based on an effective signal-to-interference-and-noise ratio for the indicator channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the indicator channel, and wherein the second error rate is based on an effective signal-to-interference-and-noise ratio for the control channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the control channel. ### Claim 17 (depends on 12) The wireless communication device of claim 12, wherein the first and second error rates are averaged over a predetermined time period. ### Claim 18 A method for radio link detection in a wireless communication system, comprising: estimating a first signal-to-interference and noise ratio (SINR) for a control channel based on one or more reference signals associated with the control channel; estimating a second SINR for an indicator channel based on one or more reference signals associated with the indicator channel, wherein the indicator channel provides an indication of a number of symbols in the control channel; generating a combined effective SINR by combining both the first SINR for the control channel with the second SINR of the indicator channel; mapping the combined effective SINR to a block error rate; determining whether a radio link problem, a radio link failure, or a radio link recovery exists based on the block error rate exceeding a threshold; and if the radio link failure exists, reporting the radio link failure. ### Claim 19 A method for radio link detection in a wireless communication system, comprising: estimating a first error rate of an indicator channel, wherein the indicator channel includes an indication of a number of symbols in a control channel; where the estimating of the first error rate is based on one or more reference signals associated with the indicator channel; estimating a second error rate of a control channel; where the estimating of the second error rate is based on one or more reference signals associated with the control channel; combining the first error rate of the indicator channel with the second error rate of the control channel to provide a combined performance metric based on both the indicator channel and the control channel; determining if a radio link problem exists based on the combined performance metric exceeding a threshold; and if the radio link problem exists, causing a subscriber station to disable transmission. ### Claim 20 A wireless communication device, comprising: a transmitter; a receiver; and a processor coupled to the receiver, wherein the processor is configured to: estimate a first error rate of an indicator channel, wherein the indicator channel includes an indication of a number of symbols in a control channel; estimate a second error rate of the control channel; where the estimate of the first and second error rates are based on one or more channel estimates; combine the first error rate of the indicator channel with the second error rate of the control channel to provide a combined performance metric based on both the indicator channel and the control channel; and detecting if a radio link problem exists based on the combined performance metric exceeding a threshold, wherein if the radio link problem exists, powering down the transmitter. ### Claim 21 A method for radio link detection in a wireless communication system, comprising: estimating a first error rate of an indicator channel, wherein the indicator channel includes an indication of a number of symbols in a control channel; where the estimating of the first error rate is based on one or more reference signals associated with the error channel; estimating a second error rate of a control channel; where the estimating of the second error rate is based on one or more reference signals associated with the control channel; combining the first and second error rates to provide a performance metric, where the first and second error rates are scaled and then added together to provide the performance metric; determining whether a radio link problem exists based on the performance metric; and when the radio link problem exists, causing a subscriber station to disable transmission. ### Claim 22 (depends on 21) The method of claim 21, further comprising: indicating a radio link problem when the performance metric is above a first threshold. ### Claim 23 (depends on 22) The method of claim 22, further comprising: indicating a radio link failure when the radio link problem persists for a first time period. ### Claim 24 (depends on 21) The method of claim 21, further comprising: indicating a radio link recovery when the performance metric is below a second threshold. ### Claim 25 (depends on 21) The method of claim 21, wherein the first and second error rates are block error rates. ### Claim 26 (depends on 21) The method of claim 21, wherein the indicator channel is a physical control format indicator channel. ### Claim 27 (depends on 21) The method of claim 21, wherein the control channel is a physical downlink control channel. ### Claim 28 (depends on 21) The method of claim 21, wherein the estimating a first error rates of an indicator channel further comprises: estimating a signal-to-interference-and-noise ratio for the indicator channel; and mapping the estimated signal-to-interference-and-noise ratio for the indicator channel to the first error rate, and wherein the estimating a second error rate of the control channel further comprises: estimating a signal-to-interference-and-noise ratio for the control channel; and mapping the estimated signal-to-interference-and-noise ratio for the control channel to the second error rate. ### Claim 29 (depends on 21) The method of claim 21, wherein the first error rate is based on an effective signal-to-interference-and-noise ratio for the indicator channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the indicator channel. ### Claim 30 (depends on 21) The method of claim 21, wherein the second error rate is based on an effective signal-to-interference-and-noise ratio for the control channel that is based on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the control channel. ### Claim 31 (depends on 21) The method of claim 21, wherein the first and second error rates are averaged over a predetermined time period. ### Claim 32 A wireless communication device, comprising: a transmitter; a receiver; and computerized logic in data communication with to the receiver and transmitter, the logic configured to enable the wireless communication device to: estimate a first error rate of an indicator channel, the indicator channel comprising an indication of a number of symbols in a control channel; estimate a second error rate of the control channel; combine the first error rate of the indicator channel with the second error rate of the control channel to provide a combined performance metric based on both the indicator channel and the control channel, the combined performance metric comprising an estimated combined Block Error Rate (BLER) of the indicator channel and the control channel; and determine whether a radio link problem exists based on at least the combined performance metric exceeding a first threshold; and wherein the logic is further configured to, when the radio link problem exists, power down the transmitter. ### Claim 33 (depends on 32) The wireless communication device of claim 32, wherein the logic is further configured to indicate a radio link failure when the radio link problem persists for at least a first time period. ### Claim 34 (depends on 32) The wireless communication device of claim 32, wherein the logic is further configured to indicate a radio link recovery when the combined performance metric is less than a second threshold. ### Claim 35 (depends on 32) The wireless communication device of claim 32, wherein the first and second error rates comprise block error rates, the indicator channel comprises a physical control format indicator channel, and the control channel comprises a physical downlink control channel. ### Claim 36 (depends on 32) The wireless communication device of claim 32, wherein the first error rate is based at least in part on an estimated signal-to-interference-and-noise ratio for the indicator channel, the estimated signal-to-interference-and-noise ratio based at least on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the indicator channel. ### Claim 37 (depends on 36) The wireless communication device of claim 36, wherein the second error rate is based at least in part on an estimated signal-to-interference-and-noise ratio for the control channel, the estimated signal-to-interference-and-noise ratio based at least on signal-to-interference-and-noise ratios for respective reference signals located on opposite sides of the control channel. ### Claim 38 (depends on 32) The wireless communication device of claim 32, wherein the logic is further configured to average the first and second error rates over a predetermined time period.