# US 8,787,143 B2 · Method and apparatus for hybrid FDM-CDM structure for single carrier based control channels > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,143 B2 - Document ID: US8787143B2 - Status: Granted - Kind: B2 - Application number: 12/443,953 - Filed: 2007-10-29 - Published: 2010-05-13 - Granted: 2014-07-22 - Earliest claimed: 2006-11-01 - Assignees: QUALCOMM Incorporated - Applicants: Durga Prasad Malladi - Inventors: Durga Prasad Malladi - Web page: https://patentgrep.com/patent/US8787143B2 ## CPC - H04L 5/0016: {Time-frequency-code} - H04J 13/0062: {Zadoff-Chu} - H04J 13/20: having an orthogonal variable spreading factor [OVSF] - H04L 5/0041: {Frequency-non-contiguous} - H04L 5/0051: {of dedicated pilots, i.e. pilots destined for a single user or terminal} - H04L 5/06: the signals being represented by different frequencies (combined with time-division multiplexing H04L5/26) - H04J 13/16: Code allocation - H04J 2013/165: {Joint allocation of code together with frequency or time} - H04L 5/0026: {Division using four or more dimensions, e.g. beam steering or quasi-co-location [QCL]} - H04L 27/2613: {Structure of the reference signals} - H04L 27/26134: {Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - 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) ## Abstract A system and method for hybrid FDM (frequency division multiplexing)-CDM (code division multiplexing) structure for single carrier control channels is provided. The hybrid FDM-CDM structure maximizes frequency diversity over the entire available bandwidth such that orthogonality between signals from users in a given cell is maintained. Thus, users in the given cell can transmit over a non-contiguous set of tones. Furthermore, the hybrid FDM-CDM structure maintains orthogonality of a pilot of users in different cells based on a despreading operation in the time domain. ## Claims ### Claim 1 An apparatus for wireless communication, comprising: means for spreading a signal from a first user in a first group of users across frequency, wherein signals from different users in the first group of users are code division multiplexed (CDM) in frequency domain; means for spreading the signal from the first user across time, wherein the signals from the different users in the first group of users are code division multiplexed in time domain; and means for mapping the signal from the first user to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed (FDM) and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 2 (depends on 1) The apparatus of claim 1, further comprising, means for mapping the signal from the first user to a set of contiguous subcarriers in a given time interval and to at least two sets of contiguous subcarriers in at least two time intervals. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the means for spreading the signal from the first user across frequency comprises means for spreading the signal from the first user based on one of a plurality of cyclic shifts of a spreading sequence to achieve CDM in the frequency domain. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the spreading sequence is a Zadoff-Chu sequence. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the means for spreading the signal from the first user across time comprises means for spreading the signal from the first user based on an orthogonal spreading code to achieve CDM in the time domain. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the orthogonal spreading code is a Hadamard code. ### Claim 7 An apparatus for wireless communication, comprising: a generating component that spreads a signal from a first user in a first group of users across frequency, spreads the signal from the first user across time, and maps the signal from the first user to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed (CDM) in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed (FDM) and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the signal from the first user comprises a control signal. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein the generating component spreads the signal from the first user based on one of a plurality of cyclic shifts of a spreading sequence to achieve CDM in the frequency domain. ### Claim 10 (depends on 9) The apparatus of claim 9, wherein the spreading sequence is a Zadoff-Chu sequence. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein the signal from the first user comprises a reference signal. ### Claim 12 (depends on 7) The apparatus of claim 7, wherein the generating component spreads the signal from the first user based on an orthogonal spreading code in time domain to achieve CDM in the time domain. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the orthogonal spreading code is a Hadamard code. ### Claim 14 (depends on 7) The apparatus of claim 7, further comprising, a transmitter to transmit the signal from the first user. ### Claim 15 (depends on 7) The apparatus of claim 7, wherein the generating component maps the signal from the first user to at least two sets of subcarriers in at least two time intervals to increase frequency diversity. ### Claim 16 (depends on 7) The apparatus of claim 7, wherein the signal from the first user has a single carrier waveform. ### Claim 17 A method for wireless communication, comprising: spreading a signal from a first user in a first group of users across frequency, wherein signals from different users in the first group of users are code division multiplexed (CDM) in frequency domain; spreading the signal from the first user across time, wherein the signals from the different users in the first group of users are code division multiplexed in time domain; and mapping the signal from the first user to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed (FDM) and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 18 (depends on 17) The method of claim 17, further comprising, mapping the signal from the first user to a set of contiguous subcarriers in a given time interval and to at least two sets of contiguous subcarriers in at least two time intervals. ### Claim 19 (depends on 17) The method of claim 17, wherein the spreading the signal from the first user across frequency comprises spreading the signal from the first user based on one of a plurality of cyclic shifts of a spreading sequence to achieve CDM in the frequency domain. ### Claim 20 (depends on 19) The method of claim 19, wherein the spreading sequence is a Zadoff-Chu sequence. ### Claim 21 (depends on 17) The method of claim 17, wherein the spreading the signal from the first user across time comprises spreading the signal from the first user based on an orthogonal spreading code to achieve CDM in the time domain. ### Claim 22 (depends on 21) The method of claim 21, wherein the orthogonal spreading code is a Hadamard code. ### Claim 23 (depends on 17) The method of claim 17, further comprising, mapping the signal from the first user to at least two sets of subcarriers in at least two time intervals to increase frequency diversity. ### Claim 24 An apparatus for wireless communication, comprising: a receiving component that obtains a received signal comprising a signal from a first user in a first group of users, the signal from the first user being spread across frequency and time and further mapped to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 25 (depends on 24) The apparatus of claim 24, further comprising, a component that demodulates the received signal. ### Claim 26 (depends on 24) The apparatus of claim 24, further comprising, a component that separates out the signals from the first group of users by employing a Fast Fourier Transform (FFT). ### Claim 27 (depends on 24) The apparatus of claim 24, further comprising, a component that recovers the signal from the first user from at least two sets of subcarriers in at least two time intervals. ### Claim 28 (depends on 24) The apparatus of claim 24, further comprising, a component that performs a despreading operation in time domain and frequency domain to recover the signal from the first user. ### Claim 29 (depends on 24) The apparatus of claim 24, further comprising, a despreading filter that employs a despreading code, which is an inverse of a spreading code employed by the first user during transmission, to recover the signal from the first user. ### Claim 30 (depends on 24) The apparatus of claim 24, wherein the signal from the first user comprises a control signal, or a reference signal, or both the control signal and the reference signal. ### Claim 31 A method for wireless communication, comprising: obtaining a received signal comprising a signal from a first user in a first group of users, the signal from the first user being spread across frequency and time and further mapped to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users; demodulating the received signal to obtain a demodulated signal; and despreading the demodulated signal in time domain and frequency domain to recover the signal from the first user. ### Claim 32 (depends on 31) The method of claim 31, further comprising, recovering the signal from the first user from at least two sets of subcarriers in at least two time intervals. ### Claim 33 (depends on 31) The method of claim 31, further comprising, applying a Fast Fourier Transform (FFT) to separate out the signals from the first group of users. ### Claim 34 A wireless communications apparatus, comprising: means for obtaining a received signal comprising a signal from a first user in a first group of users, the signal from the first user being spread across frequency and time and further mapped to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users; means for demodulating the received signal to obtain a demodulated signal; and means for despreading the demodulated signal in time domain and frequency domain to recover the signal from the first user. ### Claim 35 (depends on 34) The wireless communications apparatus of claim 34, wherein the signal from the first user has a single carrier waveform. ### Claim 36 (depends on 34) The wireless communications apparatus of claim 34, further comprising means for recovering the signal from the first user from at least two sets of subcarriers in at least two time intervals. ### Claim 37 A method for wireless communication, comprising: identifying a set of signals from users in at least one cell based in part on demodulation of a received signal, wherein a signal from each of the users is spread across frequency and time, wherein the set of signals from the users is code division multiplexed in frequency domain and time domain and is sent on a set of subcarriers corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein the set of signals from the users is frequency division multiplexed with at least one other set of signals from other users in the at least one cell, and wherein the set of signals and the at least one other set of signals are sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users; and identifying at least one signal associated with a specific user in the at least one cell based in part on a despreading operation performed on a demodulated signal in time domain and frequency domain. ### Claim 38 (depends on 37) The method of claim 37, further comprising, applying a Fast Fourier Transform (FFT) to separate out the set of signals. ### Claim 39 (depends on 37) The method of claim 37, further comprising, employing a filtering technique for performing the despreading operation. ### Claim 40 A non-transitory processor-readable medium including instructions stored thereon, comprising: instructions for spreading a signal from a first user in a first group of users across frequency; instructions for spreading the signal from the first user across time; and instructions for mapping the signal from the first user to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 41 An apparatus for wireless communication, comprising: a processor configured to: spread a signal from a first user in a first group of users across frequency, spread the signal from the first user across time, and map the signal from the first user to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available ibr assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users. ### Claim 42 (depends on 41) The apparatus of claim 41, wherein the processor is configured to spread the signal from the first user based on one of a plurality of cyclic shifts of a spreading sequence to achieve code division multiplexing in frequency domain. ### Claim 43 (depends on 42) The apparatus of claim 42, wherein the spreading sequence is a Zadoff-Chu sequence. ### Claim 44 (depends on 41) The apparatus of claim 41, wherein the processor is configured to spread the signal from the first user based on an orthogonal spreading code to achieve code division multiplexing in time domain. ### Claim 45 (depends on 44) The apparatus of claim 44, wherein the orthogonal spreading code is a Hadamard code. ### Claim 46 A wireless communications apparatus, comprising: a memory that retains instructions related to obtaining a received signal comprising a signal from a first user in a first group of users, the signal from the first user being spread across frequency and time and further mapped to a first set of subcarriers assigned to the first group of users and corresponding to a subset of a plurality of subcarriers available for assignment to users, wherein signals from different users in the first group of users are code division multiplexed in frequency domain and time domain, wherein signals from all users in the first group of users are sent on the first set of subcarriers, and wherein signals from different groups of users are frequency division multiplexed and sent on different sets of subcarriers corresponding to different non-overlapping subsets of the plurality of subcarriers available for assignment to users; and a processor coupled to the memory, configured to execute the instructions retained in the memory.