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Pilot signal

A pilot signal is a predefined reference signal of known characteristics transmitted within a communication system to assist the receiver in tasks such as synchronization, channel estimation, coherent demodulation, and signal quality monitoring.^[1]^[2] In traditional analog broadcasting, pilot signals often take the form of a single-frequency tone; for instance, in FM stereo transmission, a 19 kHz pilot tone is used to indicate the presence of a stereo signal and enable the receiver to synchronize the left and right audio channels.^[3] This approach dates back to early 20th-century radio engineering, where pilot tones facilitated supervisory control and calibration in multi-channel systems.^[4] In modern digital wireless communications, pilot signals have evolved into more structured reference signals embedded in the data stream, particularly in standards like CDMA, LTE, and 5G NR. For example, in CDMA systems, the pilot channel is an unmodulated spread-spectrum signal that provides phase references for demodulation and aids in base station selection during handoffs.^[2] In OFDM-based systems, such as those used in Wi-Fi and cellular networks, pilots are inserted at specific subcarriers to enable accurate channel estimation, compensating for fading and interference without requiring separate transmission overhead.^[5] These signals are crucial for achieving high spectral efficiency and reliability in massive MIMO and integrated sensing-communications frameworks.^[6]

Fundamentals

Definition

A pilot signal is a dedicated reference signal in telecommunications systems, typically consisting of a single frequency or a known waveform transmitted alongside the primary data-carrying signals to facilitate receiver operations such as channel estimation and phase synchronization.^[7] It is generally unmodulated or subject to minimal modulation to ensure its predictability and reliability as a benchmark.^[8] Key characteristics of pilot signals include their continuous or periodic transmission, low power levels designed to reduce interference with the main signal, and flexibility in placement either in-band (embedded within the overall signal spectrum) or out-of-band (separate from the data bandwidth).^[9] These attributes allow the signal to function effectively without disrupting payload transmission.^[4] Pilot signals differ from data signals, which encode and convey informational content, and from guard signals or bands, which primarily safeguard spectral edges against adjacent channel interference; instead, pilot signals provide a pure reference devoid of any payload data.^[10] For instance, in analog systems, a pilot may take the form of a single-tone carrier, while in digital CDMA systems, it often employs a pseudo-noise sequence for reference purposes.^[11]

Functions

Pilot signals serve several critical functions in communication systems, primarily enabling reliable signal reception and processing at the receiver. One key role is synchronization, which involves timing recovery for aligning bits or symbols and phase locking for coherent demodulation. By providing a known reference waveform, pilots allow receivers to detect the start of data frames and correct for timing offsets caused by propagation delays or clock drifts.^[12] In carrier recovery, pilots facilitate the estimation and correction of frequency and phase offsets due to oscillator imperfections or Doppler effects. The phase error is typically estimated using the argument of the product between the received pilot symbol r and the conjugate of the transmitted pilot symbol p^*, given by \theta_{\text{error}} = \arg(r \cdot p^*), assuming unit-power pilots; this enables phase-locked loops or feedforward compensators to align the local oscillator with the incoming carrier. Equalization relies on pilots for channel estimation to compensate for distortions such as fading, multipath propagation, or frequency-selective attenuation. The channel response H is computed as H = r / p, where the received pilot r is divided by the known transmitted pilot p, yielding an estimate that informs adaptive filters or zero-forcing equalizers to restore the original signal.^[13] Supervisory control uses pilots to monitor signal quality, power levels, and overall system health in real time, allowing for dynamic adjustments like power control or fault detection without interrupting data transmission.^[14] At the receiver, specific mechanisms include correlating the incoming signal with the known pilot sequence to detect its presence and estimate offsets, often achieving robust performance even in low signal-to-noise ratio (SNR) environments. Accuracy is further enhanced by averaging estimates over multiple pilot symbols, which reduces noise variance and improves the reliability of synchronization and channel parameters.^[15] These functions offer advantages such as improved effective SNR in adverse conditions through better demodulation and equalization, as well as support for adaptive modulation schemes that adjust constellation sizes based on pilot-derived channel quality assessments.^[16]

Historical Development

Origins in Analog Broadcasting

The origins of pilot signals in analog broadcasting trace back to the challenges of maintaining signal stability in vacuum tube-based systems during the early 20th century. Analog transmitters, reliant on thermionic valves, were prone to frequency drift caused by heating effects, voltage fluctuations, and component aging, which could shift carrier frequencies and degrade reception quality. Without digital stabilization techniques, broadcasters relied on manual adjustments via beat-frequency indicators or auxiliary oscillators to monitor and correct these instabilities in amplitude modulation (AM) setups from the 1920s onward.^[17]^[18] A significant advancement came with the development of frequency modulation (FM) radio in the 1930s by Edwin Howard Armstrong, whose wideband FM system reduced noise and interference but initially focused on monaural transmission. By the late 1950s, efforts to enable stereo broadcasting led to the incorporation of a 19 kHz pilot tone as a subcarrier reference, allowing receivers to detect and decode left-right audio channels while remaining compatible with mono equipment. On April 19, 1961, the Federal Communications Commission (FCC) approved this multiplex stereo standard, effective June 1, 1961, marking the formal adoption of pilot signals for FM stereo compatibility and synchronization.^[19]^[20]^[21] In television broadcasting, pilot signals emerged as essential for color synchronization with the adoption of the National Television System Committee (NTSC) standard. Approved by the FCC on December 17, 1953, the NTSC color system transmitted a 3.579545 MHz color burst—a short pilot signal consisting of 8 to 10 cycles of the chroma subcarrier—during the horizontal blanking interval of each line. This burst enabled receivers to lock onto the color reference phase, ensuring accurate demodulation of chrominance information while maintaining backward compatibility with black-and-white transmissions.^[22]^[23] Key applications extended to point-to-point links and distribution systems in the mid-20th century. During the 1940s, microwave relay networks, pioneered for telephony and early television distribution, synchronized repeaters across multi-hop paths, compensating for phase shifts and amplitude variations in high-frequency propagation. Similarly, in the 1950s, community antenna television (CATV) systems introduced pilot carriers—unmodulated tones—for automatic gain control (AGC) and automatic slope control (ASC), stabilizing signal levels against cable attenuation and temperature-induced losses in vacuum-tube amplifiers.^[24]^[25]

Evolution in Digital Systems

The transition from analog to digital telecommunications in the late 20th century marked a pivotal shift for pilot signals, adapting them from simple continuous tones used in broadcasting to more sophisticated structures integrated into digital modulation schemes. Building on analog foundations, pilot signals began supporting synchronization, channel estimation, and equalization in emerging digital systems, enabling robust performance amid noise and fading. This evolution addressed the limitations of analog pilots by incorporating them into discrete symbol streams, such as quadrature phase-shift keying (QPSK), to facilitate initial carrier recovery and phase tracking in early digital modems.^[26] In the 1980s, pilot signals were integrated into digital modulation techniques like QPSK for improved synchronization in spread-spectrum systems. A landmark demonstration occurred in November 1989 when Qualcomm showcased a terrestrial CDMA system, utilizing a dedicated pilot channel to enable power control and seamless handoffs between base stations, which were critical for maintaining signal quality in mobile environments. This approach laid the groundwork for pilot-assisted operations in code-division multiple access (CDMA) technologies. By the 1990s, standardization accelerated: the IS-95 CDMA standard, released in 1995, formalized a dedicated pilot channel transmitted continuously by base stations to provide phase reference and aid in signal acquisition without data payload, supporting voice and low-rate data services. Concurrently, the Digital Video Broadcasting - Terrestrial (DVB-T) standard, published by ETSI in 1997, introduced scattered pilots within orthogonal frequency-division multiplexing (OFDM) frames to enable channel estimation for mobile TV reception, allowing interpolation across frequency and time for robust performance in multipath channels.^[27]^[28]^[29]^[30] Entering the 2000s, pilot signal designs advanced with the rollout of 3GPP Long-Term Evolution (LTE) in Release 8 (2008), which employed common reference signals—essentially shared pilots—as cell-specific signals for downlink channel estimation in multiple-input multiple-output (MIMO) configurations, supporting up to 4x4 spatial multiplexing and enhancing throughput in frequency-selective fading. In 5G New Radio (NR), standardized in 3GPP Release 15 (2018), pilots evolved further with enhanced demodulation reference signals (DMRS) and channel state information reference signals (CSI-RS) tailored for massive MIMO and beamforming; these allow dynamic beam tracking by providing precise angular and spatial channel feedback, crucial for millimeter-wave operations. Key innovations during this period included transitioning from continuous analog-like tones to scattered pilots embedded in OFDM time-frequency grids, where pilots occupy specific subcarriers (e.g., every third or fourth in frequency) across symbols to minimize interference while enabling 2D interpolation for channel reconstruction. Additionally, compressed sensing techniques reduced pilot overhead by exploiting channel sparsity, reconstructing estimates from fewer pilots via algorithms like orthogonal matching pursuit, potentially halving transmission resources in sparse multipath scenarios without significant accuracy loss.^[31]^[32]^[33]^[34]^[35] These advancements profoundly impacted digital systems, enabling higher data rates—such as LTE's peak of 300 Mbps in early deployments—by optimizing channel estimation accuracy and reducing error floors from inter-symbol interference in high-mobility scenarios up to 350 km/h. Pilot innovations also enhanced mobility support, allowing receivers to track rapidly varying channels via frequent pilot insertions, thus mitigating Doppler effects and sustaining reliable links in vehicular and pedestrian use cases. Overall, this evolution transformed pilot signals into efficient enablers of spectral efficiency and scalability in modern wireless networks.^[36]^[37]

Applications in Analog Communications

FM Radio

In FM stereo broadcasting, the pilot signal plays a crucial role in enabling stereophonic transmission while maintaining compatibility with monophonic receivers. The standard for FM stereo, adopted by the U.S. Federal Communications Commission (FCC) in 1961 and effective from June 1 of that year, utilizes a 19 kHz pilot tone transmitted at 8% to 10% modulation depth to indicate the presence of stereo information and trigger decoding in compatible receivers. This pilot tone, derived from the 38 kHz subcarrier frequency (exactly double the pilot), allows stereo receivers to detect and process the multiplexed signal without disrupting mono playback.^[20]^[38]^[3] The transmission format involves a suppressed 38 kHz carrier modulated in double-sideband suppressed-carrier (DSB-SC) mode by the difference (L-R) audio signal, with the sum (L+R) signal occupying the main audio channel up to 15 kHz. The 19 kHz pilot tone is added to the composite baseband signal at a low level—approximately -23 dB relative to the 75 kHz maximum frequency deviation—to ensure it does not interfere with the primary audio content. This setup, standardized internationally in ITU-R Recommendation BS.450, provides backward compatibility, as monophonic receivers simply ignore the pilot and subcarrier components above 15 kHz, reproducing only the L+R signal. Additionally, the pilot tone serves as a reference for ancillary services like the Radio Data System (RDS), where the 57 kHz RDS subcarrier is phase-locked to the third harmonic of the 19 kHz pilot for stable data transmission.^[3] In the receiver, a phase-locked loop (PLL) circuit locks onto the 19 kHz pilot tone, which is then frequency-doubled to regenerate the precise 38 kHz subcarrier for demodulating the L-R sidebands and reconstructing the left and right channels. The pilot's low injection level preserves mono compatibility by minimizing audible distortion in non-stereo equipment, a key design principle that facilitated widespread adoption of stereo FM without obsoleting existing receivers. Technical specifications mandate a pilot frequency tolerance of ±2 Hz to ensure reliable locking and avoid decoding errors, with the overall system deviation limited to ±75 kHz for 100% modulation.^[38]^[3]

AM Stereo Radio

AM stereo radio systems utilized pilot signals to enable stereophonic broadcasting on amplitude modulation (AM) carriers while maintaining compatibility with monaural receivers. These systems emerged in the late 1970s and 1980s as broadcasters sought to enhance AM audio quality amid growing FM popularity. The pilot tone, typically a low-frequency subaudible signal, informed stereo receivers of the presence of left-right (L-R) channel information, allowing separation of the stereo signal without distorting the sum (L+R) mono content detectable by standard envelope detectors.^[39] The dominant system, Compatible Quadrature Amplitude Modulation (C-QUAM), developed by Motorola in the 1970s, became the de facto and later official standard for AM stereo in the United States and Canada. In C-QUAM, the L+R signal amplitude-modulates the carrier in the conventional manner, while the L-R signal phase-modulates it in quadrature (90 degrees offset), ensuring mono compatibility. A 25 Hz pilot tone, injected into the L-R channel, serves as a reference for stereo detection; its presence triggers the receiver's decoder to extract the quadrature component. The pilot's amplitude is set to produce 5% modulation of the maximum allowable L-R deviation when the carrier is unmodulated, and it varies inversely with the overall amplitude modulation to preserve signal balance. This low-level pilot—typically 5-10% of the carrier amplitude—avoids audible interference in mono reception while enabling phase-locked recovery of the stereo information.^[40]^[39] Competing systems in the 1970s and early 1980s included the Kahn/Hazeltine independent sideband (ISB) approach, which used a 15 Hz pilot tone to synchronize the receiver's decoding of separately modulated upper and lower sidebands for L and R channels, and the Magnavox phase-modulation system, employing a 5 Hz pilot modulated at ±20 Hz for stereo identification. The Harris system initially used a distinct pilot but later adjusted to 25 Hz for interoperability with C-QUAM. In all cases, the pilot modulated a compatible carrier component, with receivers combining envelope detection for L+R and pilot-guided phase or sideband separation for L-R. Phase shift keying encoded the L-R information relative to the pilot reference, achieving separation ratios of 20-25 dB across the audio band up to 5 kHz.^[41]^[42] Implementation challenges arose from the need for precise quadrature alignment and low pilot power to ensure 100% mono compatibility, as higher levels could introduce distortion in legacy receivers. The Federal Communications Commission (FCC) initially allowed a "marketplace" approach in 1982, permitting multiple systems, but protracted patent disputes—particularly between Kahn and Motorola—delayed widespread adoption. By 1993, C-QUAM was formalized as the U.S. standard, yet only about 600 stations broadcast in AM stereo, primarily in the U.S. and parts of Europe. The format faded by the late 1990s due to FM's superior fidelity and stereo prevalence, limited AM bandwidth (typically 10 kHz), and the shift toward digital broadcasting, rendering pilot-based AM stereo largely obsolete.^[39]

Television Broadcasting

In analog television broadcasting, pilot signals play a crucial role in synchronizing color and timing information during over-the-air transmission. The color burst serves as a primary pilot for chrominance phase reference, transmitted as short bursts of the color subcarrier during the horizontal blanking interval. In the NTSC standard, this burst operates at a frequency of 3.579545 MHz with a phase of 180°, consisting of approximately 8 cycles for a duration of about 2.25 μs, and has a peak-to-peak amplitude of 40 IRE units centered on the blanking level.^[22]^[23]^[43] Similarly, the PAL standard employs a color burst at 4.43361875 MHz, with a duration of 2.25 ± 0.23 μs encompassing 10 ± 1 cycles, positioned 5.6 ± 0.1 μs after the start of the horizontal sync pulse.^[44] These bursts, typically at 10-20% of the luminance signal amplitude relative to the full video excursion, enable receivers to regenerate the subcarrier accurately, ensuring color fidelity across transmission channels despite potential phase shifts from propagation delays.^[45] Horizontal and vertical sync pulses function as additional pilot signals for timing synchronization in analog TV systems. The horizontal sync pulses, occurring at 15.734 kHz in NTSC, mark the start of each scan line, while vertical sync pulses at 60 Hz delineate field boundaries, allowing receiver deflection circuits to align precisely with the transmitted frame.^[23] The envelope of the color burst also serves a detection role; its presence indicates a color transmission, triggering the receiver's color processing circuits, whereas its absence activates a color killer to suppress chroma demodulation and avoid noise artifacts in monochrome content.^[46] In television receivers, automatic phase control (APC) circuits lock onto the color burst to maintain subcarrier synchronization. These circuits compare the incoming burst phase with a locally generated oscillator, adjusting for any discrepancies to regenerate the chrominance subcarrier stably, thus preventing hue errors.^[47] The NTSC color standard, incorporating these pilot mechanisms, was adopted by the FCC on December 17, 1953, following extensive field tests and refinements to ensure compatibility with existing monochrome receivers.^[48] In contrast, the SECAM variant, developed as an alternative European standard, employs frequency modulation of two color-difference carriers without a discrete color burst pilot, relying instead on line-sequential transmission for phase stability.^[49] This design choice in SECAM avoids the need for burst-based synchronization but requires memory circuits in receivers to reconstruct the full color image.

Video and Cable Systems

In analog video cassette recorders (VCRs) utilizing helical scan technology, pilot signals are recorded as control track pulses along the tape's linear edge to ensure precise servo timing and playback speed control. These pulses, typically a 30 Hz square wave in NTSC systems, are derived from the vertical sync of the input video signal and recorded simultaneously with the helical video tracks.^[50] The control track head reads these pulses during playback, comparing their phase and frequency to a stable 30 Hz reference signal generated by the VCR's circuitry. This comparison drives a servo loop that adjusts the capstan motor speed, maintaining uniform tape transport and aligning the rotating video heads with the slanted helical tracks for stable image reproduction.^[50] The pilot frequency directly corresponds to the capstan's rotational speed, which is set to advance the tape by one field per pulse in NTSC format, preventing speed variations that could cause jitter or skew in the reproduced video. In cable television (CATV) distribution networks, pilot tones serve as unmodulated carriers inserted at the headend to maintain signal integrity across coaxial amplifiers and trunks. These tones enable automatic gain control (AGC) in amplifiers by providing a stable reference for level stabilization against temperature fluctuations and cable losses, while a second tone facilitates slope equalization to compensate for frequency-dependent attenuation in the mid-to-high bands.^[51] For example, in U.S. systems, pilots are often placed at mid-band frequencies such as 166.5 MHz to minimize interference with video channels and FM carriers, ensuring the tone remains isolated from modulated signals.^[52] Insertion levels at the headend are typically maintained between 10 and 32 dBmV for forward-path pilots, allowing amplifiers to monitor and adjust overall signal tilt and amplitude over long coaxial runs without introducing distortion.^[53] The use of pilot signals in both VCRs and CATV systems peaked during the 1970s and 1980s, coinciding with the widespread adoption of consumer VCRs and expanded analog cable networks. Innovations like dual pulsed-pilot carriers for CATV amplifiers, introduced in the early 1970s, improved temperature and color stability by dynamically adjusting gain at low- and high-band frequencies.^[54] By the 1990s, these analog techniques remained prominent in legacy setups but were gradually phased out as digital video standards, such as DVD and digital cable modulation, eliminated the need for continuous-tone references in favor of embedded synchronization in packetized streams.^[51] Today, pilot signals persist only in specialized analog maintenance or hybrid legacy-digital environments for backward compatibility.

Applications in Digital Communications

Wireless and Cellular Networks

In code-division multiple access (CDMA) systems standardized as IS-95, the pilot channel, designated as channel 0, transmits a continuous stream of all-zero data using the all-zero Walsh code to serve as a reference for mobile stations.^[55] This unmodulated signal enables initial acquisition of the base station's timing, facilitates power control by allowing mobiles to measure received signal strength, supports soft handoff decisions during mobility, and provides phase reference for rake receiver finger timing to combine multipath components.^[56] Deployed commercially in the mid-1990s, such as South Korea's nationwide rollout in 1996, the pilot channel was integral to CDMA's soft handoff mechanism, which allows seamless transitions between cells by maintaining connections with multiple base stations simultaneously.^[57] The Universal Mobile Telecommunications System (UMTS) based on wideband CDMA (WCDMA) employs the common pilot channel (CPICH), specifically the primary CPICH, which broadcasts a predefined bit sequence at a fixed transmit power level set by the network.^[58] This channel aids user equipment in cell search by detecting the primary scrambling code, performs channel estimation for coherent demodulation of other downlink channels, and supports handover measurements.^[59] As a cell-wide reference, the CPICH operates without user-specific modulation, ensuring reliable synchronization across the coverage area. In Long-Term Evolution (LTE) networks, cell-specific reference signals (CRS) function as pilot signals embedded within resource blocks across the downlink subframe.^[60] Transmitted from each antenna port, CRS enable user equipment to perform channel estimation for coherent demodulation of physical downlink shared channels and to conduct measurements for mobility management, such as reference signal received power and quality.^[61] These pilots are crucial for supporting multiple-input multiple-output (MIMO) configurations, as they allow estimation of the channel matrix across transmit antennas, thereby enabling spatial multiplexing and diversity gains in multi-antenna deployments.^[62] Fifth-generation New Radio (5G NR) introduces more flexible pilot structures to accommodate massive MIMO and beamforming. The synchronization signal block (SSB) includes pilot-like components within the primary and secondary synchronization signals and demodulation reference signals (DMRS) for the physical broadcast channel, supporting initial cell acquisition and beam management by allowing user equipment to identify optimal beams during alignment.^[63] Additionally, DMRS are transmitted on a per-user basis, associated with specific physical downlink channels like the physical downlink shared channel, to enable precise channel estimation tailored to individual user equipment mobility and beam configurations.^[64] Across these cellular standards, pilot signals introduce an overhead typically ranging from 10% to 20% of the base station's transmit power or resource allocation, balancing the need for robust channel estimation—essential for reliable data demodulation—with spectral efficiency. This overhead supports key functions like those in rake receivers or MIMO processing without dominating the overall capacity.

Satellite and OFDM Systems

In satellite communication systems, such as those defined by the Digital Video Broadcasting - Satellite (DVB-S) and DVB-S2 standards, continual pilot symbols are inserted periodically within the physical layer frame (PLFRAME) to facilitate carrier phase recovery at the receiver. These pilots consist of 36 unmodulated symbols placed every 16 slots (or 1,440 symbols) following the PLHEADER, providing a regular reference for synchronization in the presence of phase noise and oscillator instabilities. This structure incurs approximately 2.4% overhead but is optional, allowing pilot-less modes for higher efficiency in stable channels. For time-variant channels, such as those encountered in mobile satellite links, these pilots also support equalization by enabling estimation of channel variations over the frame duration.^[65] In the Global Positioning System (GPS), pilot signals based on pseudorandom noise (PRN) codes are employed for code acquisition and tracking, particularly in modern signals like L1C and L5. The pilot channel, which is dataless, carries the PRN sequence to aid initial signal detection and coherent demodulation without data interruptions, enhancing robustness in weak signal environments typical of satellite navigation. Similarly, Inmarsat systems, operational since the 1980s, incorporate pilot tones or signals for link budget monitoring and automatic gain control (AGC), ensuring reliable performance in maritime and aeronautical applications by compensating for propagation losses and fading. These pilot tones, often transmitted at the center of the transponder bandwidth, allow real-time assessment of signal strength and channel conditions.^[66]^[67] Orthogonal frequency-division multiplexing (OFDM) systems, widely used in wireless local area networks (WLANs) under IEEE 802.11a/g standards, rely on dedicated pilot subcarriers and training sequences for channel estimation and synchronization. The preamble includes short training symbols for fast Fourier transform (FFT) timing and coarse frequency offset correction, followed by long training symbols (LTS) for fine synchronization and initial channel estimation across all subcarriers. During data transmission, four fixed pilot subcarriers at positions -21, -7, 7, and 21 carry known BPSK-modulated symbols to track residual phase and frequency offsets, enabling ongoing channel interpolation. The channel frequency response at pilot subcarriers k is estimated using the least-squares method:

\hat{H}_k = \frac{Y_k}{X_k}

where Y_k is the received symbol and X_k is the known transmitted pilot symbol, providing a simple yet effective reference for equalizing the OFDM subchannels.^[68] In mobile television standards like DVB-T and DVB-H, two-dimensional scattered pilots are arranged in a grid pattern across both time and frequency domains to handle dynamic channel impairments, including Doppler shifts from receiver motion. These pilots occupy every 12th carrier, shifted by 3 positions per symbol, forming a diagonal pattern that constitutes approximately 8% overhead, while continual pilots at fixed carrier indices (e.g., 45 in 2K mode) address phase noise with about 2.6% additional overhead. This configuration allows receivers to interpolate channel estimates in two dimensions, effectively tracking time-varying fades and improving performance in vehicular environments. Overall, pilot signals in these satellite and OFDM systems mitigate multipath fading and Doppler effects, reducing bit error rate (BER) by 1-2 dB compared to non-pilot-aided schemes, particularly in mobile satellite scenarios where signal attenuation can exceed 20 dB.^[69]

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[44]
PAL video timing specification
Burst start 5.6 +- 0.1 us after sync start. Burst 10 +- 1 cycles. Video signal. a = line sync b = back porch. There are various Video/Television standards in ...
[45]
[PDF] NTSC-M Color Television Specifications - The AM Stereo Tech Zone™
For digital encoding in the studio all timing components of the composite signal are synchronized to the master clock and for digital decoding in the receiver ...
[46]
[PDF] Basic Television, Bernard Grob
The loss of color hold can be caused by an inoperative burst amplifier, resulting in no color sync voltage, or a defect in the automatic-phase-control circuit.
[47]
[PDF] Colour Television - World Radio History
which compares the oscillator and burst signals. This arrangement is usually called an A.P.C. loop, that is, an automatic phase control. Page 294. 272. COLOUR ...
[48]
Milestones:Monochrome-Compatible Electronic Color Television ...
Dec 3, 2024 · After RCA carried out more field tests, the NTSC forwarded this standard to the FCC in a petition on July 22, 1953. The FCC approved the ...
[49]
SECAM Technology - Rohde & Schwarz
SECAM is a French standard using two FM carriers to carry color-difference signals, creating a composite color video signal. It is used in France and former ...Missing: pilot | Show results with:pilot
[50]
[PDF] MAINTENANCE FUNDAMENTALS OF 3/4-INCH VIDEO CASSETTE
The signal recorded on the control track is normally a 30 Hz signal; however, on some early machines, this signal was recorded at 60 Hz. This signal, when used ...
[51]
[PDF] The History of Modern Cable Television Technology
Modern amplifiers use a pilot signal to regulate Automatic. Gain Control, AGC, circuits. A second pilot signal. Page 8. 8 at a substantially different ...
[52]
Mid-Band Use In CATV Systems - NCTA Technical Papers
No attempt was made to use mid-band frequencies above 157.25 MHz (Channel "G") in order to avoid interference with the 166.5 MHz pilot carrier used in the ...Missing: tone | Show results with:tone
[53]
[PDF] :DQ. THIS PAGL - OSTI
The trunk signal level should be maintained at 10 to 32 dBmV for the forward pilot carriers and 15 to 35 dBmV for the reverse pilot carriers. (where applicable) ...
[54]
[PDF] dual pulsed-pilot .. carrier alc for temperature and
The most practical ALC method is to employ two pilot carriers, one at high band and one at low band o Any tilt variations caused by cable characteristics, ...
[55]
[PDF] chapter 8 - cdma technology, is-95, and imt-2000 - CWINS
and fading, implements soft handoffs, has less power consumption (6-7 mW on aver- age), that is, about 10 percent of analog or TDMA phones because of ...
[56]
[PDF] Soft Handoff and Power Control in IS-95 CDMA
Dec 6, 1999 · Because there are three fingers of the RAKE receiver in the mobile, the active set size is a maximum of three pilots. IS-95 allows up to six ...Missing: zero | Show results with:zero
[57]
Milestones:Large-Scale Commercialization of a CDMA Cellular ...
Oct 4, 2024 · But in CDMA, digital signal processing and soft handover were employed. Furthermore, the component technology, power control, suppression of ...
[58]
[PDF] TSGR1#16(00)1258 - 3GPP
The Primary Common Pilot Channel (P-CPICH) has the following characteristics: - The same channelization code is always used for the P-CPICH, see [4];. - The P- ...
[59]
Pilot power optimization and coverage control in WCDMA mobile ...
Pilot power is the most important parameter that allows us to control the strength of the CPICH signal. The more power is spent for pilot signals, the better ...<|control11|><|separator|>
[60]
[PDF] TS 136 211 - V15.4.0 - LTE - ETSI
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or. GSM identities. These should be ...Missing: pilots | Show results with:pilots
[61]
Understanding and Demodulating LTE Signals - MATLAB & Simulink
Marked in white are Cell-Specific Reference Signals (CRS), which are pilot symbols used for coherent demodulation. ... Figure 6 shows the correlation result ...
[62]
A primer on MIMO in LTE - EDN Network
Feb 1, 2010 · In LTE, reference signals (or pilots) at regular frequency locations in the output of each transmitter provide a way for the receivers to ...
[63]
A comprehensive study on the synchronization procedure in 5G NR ...
Oct 27, 2023 · 5G NR has introduced a key element, the synchronization signal block (SSB). ... Demodulation reference signals (DMRS) for PBCH. DMRS is introduced ...
[64]
Demodulation Reference Signals (DMRS) in 5G NR - MATLAB
Aug 28, 2019 · DM-RS are used for channel estimation and demodulation of associated physical channels. They can also be used to estimate receive signal power.
[65]
[PDF] EN 302 307 - V1.3.1 - Digital Video Broadcasting (DVB) - ETSI
Carrier recovery in the receivers may be facilitated by the introduction of a regular raster of pilot symbols. (P = 36 pilot symbols every 16 SLOTs of 90 ...
[66]
GPS Signal Plan - Navipedia - GSSC
The Coarse/Acquisition (C/A) code signal was primarily thought for acquisition of the P (or Y) code and has become nowadays the most important signal for mass ...
[67]
[PDF] N9 '22771
the airline companies in order to maintain customer satisfaction and allegiance. Since 1991, Inmarsat has provided a single channel ... a data and a pilot signal ...
[68]
Preamble and pilot symbol design for channel estimation in OFDM ...
Jun 3, 2011 · Power of the preamble and pilot symbols designed by the l 2 norm for L = N p = 4 at 10 dB (IEEE 802.11a). Full size image. We also consider a ...
[69]
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