Showing papers on "Spectral efficiency published in 1979"
TL;DR: In this paper, the co-channel interference probabilities for mobile radio systems operating in a Rayleigh fading lognormal shadowing environment with inverse fourth power law dependence of area mean signal level on range were calculated.
Abstract: Co-channel interference probabilities are calculated for mobile radio systems operating in a Rayleigh fading lognormal shadowing environment with inverse fourth power law dependence of area mean signal level on range. Interference levels are shown to be high even with generous reuse distances. The results are used to calculate spectrum utilization using reasonable but tentative estimates of protection ratio and channel spacing for SSB systems. On this basis SSB offers a higher spectral efficiency than current 25 kHz spaced FM systems.
161 citations
TL;DR: In this article, the spectrum efficiency of a frequency-hopped-DPSK spread-spectrum modulation technique proposed for use in urban mobile radio systems is estimated based on simple models for the factors influencing system performance, and requires no computer simulation.
Abstract: The spectrum efficiency (bits/s per unit bandwidth) of a frequency-hopped-DPSK spread-spectrum modulation technique proposed for use in urban mobile radio systems is estimated. The analysis is based on simple models for the factors influencing system performance, and requires no computer simulation. It permits straightforward evaluation of spectrum efficiency over a broad range of system parameters. For an isolated service area (cell) with no propagation impairments, the efficiency is 0.12 at a bit error rate of 10-3. When interference from nearby cells is considered (assuming centrally located base stations with omni-directional antennas), the efficiency falls to 0.03 - 0.06, depending on how much performance degradation can be tolerated near the cell boundaries. Finally, the effects of multipath (Rayleigh) fading reduce system efficiency to 0.02 - 0.05.
45 citations
TL;DR: A novel long haul 5 GHz 16 QAM digital radio system, which has 200 Mbit/s transmission capacity within the 40 MHz interleaved channel allocation, is proposed and described, and a new signal shaping filter, differential encoding and carrier recovery techniques are presented.
Abstract: A novel long haul 5 GHz 16 QAM digital radio system, which has 200 Mbit/s transmission capacity within the 40 MHz interleaved channel allocation, is proposed and described. It is designed to be overbuilt on existing FDM-FM routes with an approximately 50 km repeater spacing. To achieve the 5 bit/s/Hz RF spectral efficiency, the 16 QAM modulation and Nyquist cosine roll-off spectral shaping techniques ( \alpha = 0.5 ) are investigated. Then a new signal shaping filter, differential encoding and carrier recovery techniques are presented. Finally, the effects of TWT amplifier nonlinearity on a 16 QAM signal are experimentally investigated.
31 citations
TL;DR: Computer simulation results are presented for a MSK system and an Offset QPSK system, both filtered for 0%, 50% and 100% excess bandwidth raised cosine spectrum, and it is shown that when filtered to give the same spectrum the different system have identical P e versus S/N performance.
Abstract: In this paper a model of Minimum Shift Keying (MSK) is introduced, an analysis of which shows that the theoretical maximum bandwidth efficiency of MSK is 2 bits/s/Hz, the same as for Quadrature Phase Shift Keying (QPSK) and Offset Quadrature Phase Shift Keying (Offset QPSK). The filtering necessary to achieve minimum spectrum width as well as a raised cosine spectrum while maintaining the condition of zero intersymbol interference for Offset QPSK is reviewed, and the equivalent filtering for MSK derived. In addition, partioning of this filtering between transmitter and receiver for optimum probability of error (P e ) versus receiver input signal to noise ( S/N ) ratio is given. Computer simulation results are presented for a MSK system and an Offset QPSK system, both filtered for 0%, 50% and 100% excess bandwidth raised cosine spectrum. The results show fully open eyes at the decision threshold input for all cases. They also show that when filtered to give the same spectrum the different system have identical P e versus S/N performance, S/N being defined at the input to the receiver decision threshold, i.e., after all the filtering for the desired raised cosine spectrum. This performance is best for 100% excess bandwidth filtering and worst for 0% excess bandwidth filtering.
29 citations
27 Mar 1979
TL;DR: In this article, the authors estimate the spectrum efficiency of a Frequency-Hopped-DPSK modulation technique proposed for use in urban mobile radio systems, based on simple models for the factors influencing system performance, and require no computer simulations.
Abstract: We estimate the spectrum efficiency (bits/sec. per unit bandwidth) of a Frequency-Hopped-DPSK modulation technique proposed for use in urban mobile radio systems. The analysis is based on simple models for the factors influencing system performance, and requires no computer simulations. It permits straightforward evaluation of spectrum efficiency over a broad range of system parameters. For an isolated service area (cell) with no propagation impairments, the efficiency is 0.12 at a bit error rate of 10-3. When interference from nearby cells is considered (assuming centrally located base stations with omnidirectional antennas), the efficiency falls to 0.03 - 0.05, depending on how much performance degradation can be tolerated near the cell boundaries. Finally, the effects of multipath (Rayleigh) fading reduce system efficiency to 0.02 - 0.04.
13 citations
TL;DR: It is shown that 4 level FM is able to provide good spectral efficiency without requiring modification or replacement of most current FM radios, and is relatively insensitive to the transmission degradations typically encountered in fielded systems.
Abstract: This paper explores the feasibility of using 4 level FM to enable digital transmission with a spectrum efficiency on the order of two bits per cycle of transmitted bandwidth when used with Frequency Modulated (FM) radios A hybrid computer simulation was used to assess the compatibility of 4 level FM with the transfer characteristics of commercial FM radios and also to evaluate the performance of 4 level FM modulation under conditions of radio misalignment It is shown that 4 level FM is able to provide good spectral efficiency without requiring modification or replacement of most current FM radios, It is also shown that 4 level FM performance is relatively insensitive to the transmission degradations typically encountered in fielded systems
2 citations
01 Oct 1979
TL;DR: The bit–error–probability performances of HF digital radio systems with respect to channel and equipment additive, multiplicative, and nonlinear distortions are evaluated and the best combination of system design features is determined.
Abstract: The bit–error–probability performances of HF digital radio systems with respect to channel and equipment additive, multiplicative, and nonlinear distortions are evaluated with respect to the nine system design features that affect the performances. The system design features are the fundamental pulse waveform, the keying method (ASK, PSK, APSK, FSK, and CPK), the multiplexing method (frequency and concentric multiplexing ), the type of demodulator filter (matched and nonmatched nonadaptive filters and quasi–static and dynamic adaptive filters ), the detection method (coherent, partially coherent, differentially coherent and noncoherent), the transmitter power, the antennas, diversity, and error coding. Spectral efficiency (information rate/signal bandwidth) is also evaluated. The best combination of system design features is determined.
2 citations
27 Mar 1979
TL;DR: The paper discusses the implications of channel splitting and examines the objections which have been raised against reducing channel widths below 25 kHz and shows clearly that spectrum efficiency is improved as bandwidths are reduced.
Abstract: The paper discusses the implications of channel splitting and examines the objections which have been raised against reducing channel widths below 25 kHz. It shows that, although the intermodulation products multiply in number, with suitable planning procedures the increase, if anything, tends to improve the choice of frequencies to be allocated. This is particularly so in the case of two frequency operation. Reuse is examined in relation to various layout configurations and shows clearly that spectrum efficiency is improved as bandwidths are reduced.
2 citations