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    "title": "Alamouti: two transmit antennas help a single receiver withstand fading",
    "summary": "Alamouti's1998 paper couples a two-antenna transmission sequence with simple receiver combining to obtain transmit diversity without channel feedback to the transmitter, under its coherent block-fading assumptions.\n\nWireless signals can weaken when reflected paths cancel. Instead of putting two antennas into every receiving device, this construction spreads a pair of symbols across two transmitter antennas and two symbol periods; the receiver combines the observations using its channel estimates. It can obtain the same diversity order as two-branch receive combining, and extends to multiple receive antennas. Diversity order describes resilience to fading, not identical error rates or free extra transmission power.",
    "boundary": "The exact target is the two-transmit-antenna encoding/combining/detection construction and its one/M-receiver extension in Section III, with the 1998 paper's stated coherent-channel conditions. The channel is assumed constant across the two consecutive encoded symbol periods, and receiver channel knowledge is needed even though no receiver-to-transmitter channel feedback is required. The 2 M diversity order and reference error-rate comparisons rely on the stated independent/uncorrelated fading setting; no guarantee for arbitrary correlated or fast-varying channels is admitted. Section IV assumes uncorrelated Rayleigh amplitudes, equal average branch powers and perfect channel knowledge. Equal diversity order does not imply equal BER at equal total radiated power: the paper reports a 3 d B disadvantage against the specified MRRC comparison when total transmit power is held fixed. Pilot-based channel estimation needs extra pilots; the time-domain scheme has a two-symbol decoding delay. 'No bandwidth expansion' is not absence of hardware, channel-estimation or energy cost. Antenna spacing suggestions are environment-dependent, not universal design rules; interference-cancellation effects are explicitly unresolved. Earlier transmit-diversity and space-time trellis schemes, and later general orthogonal designs and standards, remain distinct contributions.",
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      "scope": "Supplies an explicit two-transmitter symbol sequence and simple coherent combiner, with a receiver-count diversity extension and implementation/power qualifications. The exact target is the two-transmit-antenna encoding/combining/detection construction and its one/M-receiver extension in Section III, with the 1998 paper's stated coherent-channel conditions. The channel is assumed constant across the two consecutive encoded symbol periods, and receiver channel knowledge is needed even though no receiver-to-transmitter channel feedback is required. The 2 M diversity order and reference error-rate comparisons rely on the stated independent/uncorrelated fading setting; no guarantee for arbitrary correlated or fast-varying channels is admitted. Section IV assumes uncorrelated Rayleigh amplitudes, equal average branch powers and perfect channel knowledge. Equal diversity order does not imply equal BER at equal total radiated power: the paper reports a 3 d B disadvantage against the specified MRRC comparison when total transmit power is held fixed. Pilot-based channel estimation needs extra pilots; the time-domain scheme has a two-symbol decoding delay. 'No bandwidth expansion' is not absence of hardware, channel-estimation or energy cost. Antenna spacing suggestions are environment-dependent, not universal design rules; interference-cancellation effects are explicitly unresolved. Earlier transmit-diversity and space-time trellis schemes, and later general orthogonal designs and standards, remain distinct contributions.",
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            "citation": "Siavash M. Alamouti, A Simple Transmit Diversity Technique for Wireless Communications, IEEE JSAC16(8)(October1998),1451–1458",
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        "description": "The exact target is the two-transmit-antenna encoding/combining/detection construction and its one/M-receiver extension in Section III, with the 1998 paper's stated coherent-channel conditions. The channel is assumed constant across the two consecutive encoded symbol periods, and receiver channel knowledge is needed even though no receiver-to-transmitter channel feedback is required. The 2 M diversity order and reference error-rate comparisons rely on the stated independent/uncorrelated fading setting; no guarantee for arbitrary correlated or fast-varying channels is admitted. Section IV assumes uncorrelated Rayleigh amplitudes, equal average branch powers and perfect channel knowledge. Equal diversity order does not imply equal BER at equal total radiated power: the paper reports a 3 d B disadvantage against the specified MRRC comparison when total transmit power is held fixed. Pilot-based channel estimation needs extra pilots; the time-domain scheme has a two-symbol decoding delay. 'No bandwidth expansion' is not absence of hardware, channel-estimation or energy cost. Antenna spacing suggestions are environment-dependent, not universal design rules; interference-cancellation effects are explicitly unresolved. Earlier transmit-diversity and space-time trellis schemes, and later general orthogonal designs and standards, remain distinct contributions.",
        "domain": "Wireless communications"
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        {
          "citation": "Siavash M. Alamouti, A Simple Transmit Diversity Technique for Wireless Communications, IEEE JSAC16(8)(October1998),1451–1458",
          "url": "https://www.ece.tufts.edu/ee/108/alamouti.pdf"
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      "statement": "# Alamouti: two transmit antennas help a single receiver withstand fading\n\nAlamouti's1998 paper couples a two-antenna transmission sequence with simple receiver combining to obtain transmit diversity without channel feedback to the transmitter, under its coherent block-fading assumptions.\n\nWireless signals can weaken when reflected paths cancel. Instead of putting two antennas into every receiving device, this construction spreads a pair of symbols across two transmitter antennas and two symbol periods; the receiver combines the observations using its channel estimates. It can obtain the same diversity order as two-branch receive combining, and extends to multiple receive antennas. Diversity order describes resilience to fading, not identical error rates or free extra transmission power.\n\n## Scientific scope\n\nThe exact target is the two-transmit-antenna encoding/combining/detection construction and its one/M-receiver extension in Section III, with the 1998 paper's stated coherent-channel conditions. The channel is assumed constant across the two consecutive encoded symbol periods, and receiver channel knowledge is needed even though no receiver-to-transmitter channel feedback is required. The 2 M diversity order and reference error-rate comparisons rely on the stated independent/uncorrelated fading setting; no guarantee for arbitrary correlated or fast-varying channels is admitted. Section IV assumes uncorrelated Rayleigh amplitudes, equal average branch powers and perfect channel knowledge. Equal diversity order does not imply equal BER at equal total radiated power: the paper reports a 3 d B disadvantage against the specified MRRC comparison when total transmit power is held fixed. Pilot-based channel estimation needs extra pilots; the time-domain scheme has a two-symbol decoding delay. 'No bandwidth expansion' is not absence of hardware, channel-estimation or energy cost. Antenna spacing suggestions are environment-dependent, not universal design rules; interference-cancellation effects are explicitly unresolved. Earlier transmit-diversity and space-time trellis schemes, and later general orthogonal designs and standards, remain distinct contributions.\n\n## People and systems\n\nSiavash M. Alamouti\n\n\n\n## Original sources\n\n- [Siavash M. Alamouti, A Simple Transmit Diversity Technique for Wireless Communications, IEEE JSAC16(8)(October1998),1451–1458](https://www.ece.tufts.edu/ee/108/alamouti.pdf)\n",
      "summary": "Alamouti's1998 paper couples a two-antenna transmission sequence with simple receiver combining to obtain transmit diversity without channel feedback to the transmitter, under its coherent block-fading assumptions.\n\nWireless signals can weaken when reflected paths cancel. Instead of putting two antennas into every receiving device, this construction spreads a pair of symbols across two transmitter antennas and two symbol periods; the receiver combines the observations using its channel estimates. It can obtain the same diversity order as two-branch receive combining, and extends to multiple receive antennas. Diversity order describes resilience to fading, not identical error rates or free extra transmission power.",
      "title": "Alamouti: two transmit antennas help a single receiver withstand fading"
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    "title": "Alamouti: two transmit antennas help a single receiver withstand fading",
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    "what_changed": "Supplies an explicit two-transmitter symbol sequence and simple coherent combiner, with a receiver-count diversity extension and implementation/power qualifications.",
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        "title": "Siavash M. Alamouti, A Simple Transmit Diversity Technique for Wireless Communications, IEEE JSAC 16(8)(October 1998),1451–1458",
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