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Guard time length (GT) is one of the key OFDMA parameters. It is implemented as cyclic prefix (CP) to completely alleviate intersymbol interference (ISI) and to preserve orthogonality among OFDMA subcarriers as long as the guard time length is sufficiently greater than channel delay spread. In conventional OFDMA systems a fixed GT length is chosen...
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Work reported herein contributes to the prediction of achievable performance of the IEEE 802.16 standard using time series of 50 Mchps PN channel sounder measurements at 4.9 GHz on radio channels in a scenario in which emergency vehicles are parked outside a building and operate as a centre for communications with rescue crews and equipment inside...
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... The Guard Time (GT) length is selected such that the symbol time is greater than the channel delay spread of 8μs. Practically, the GT length is 25% of the useful symbol time, which implies a 1 dB reduction in the SNR, so GT length is two or four times the maximum anticipated delay spread [6]. In the present design, the maximum SNR loss is 0.97 dB, due to the inclusion of GT. ...
... MIMO wireless systems with multiple antennas at both transmitter and receiver sides operate by increasing the number of antennas at both the transmitter and the receiver to satisfy the high capacity requirements of wireless systems. As the number of transmit antennas 'Nt' and number of receive antennas 'Nr', satisfy the condition Nr≥ Nt, there is a linear increase in capacity [6]. When using spatial multiplexing for a data rate per stream 'R', the number of transmit antennas 'Nt', the transmit data rate is Nt x R. The same information is sent through signals along different paths and multiple independently faded replicas of the data symbol are combined at the receiver. ...
... Practically the CP has to be either 2-4 times the maximum anticipated delay-spread or kept to 25% of T b [8]. The authors of both [9] and [10] have used a guard time duration of two and three times, respectively, the propagation delay corresponding to the difference in fiber lengths between the RAUs. ...
In this paper we investigate protocol issues that might arise due to the extra fiber propagation delay in fiber-fed IEEE 802.16m networks. Our study indicates that although the fiber delay might affect network performance, an informed choice of protocol parameters, such as the guard times and the ranging channel structure, can minimize the reduction in efficiency and allow for relaxation of some of the constraints imposed on the optical distribution network architecture.
... ∆L max ), that can be accommodated by each of the CP durations so that no optical multipath interference exists, can be calculated. Practically the CP duration has to be either 2-4 times the maximum anticipated delay-spread or kept to 25% of the useful symbol time [12]. The authors of both [13] and [14] have used a CP duration of 2 and 3 times, respectively, the propagation delay corresponding to the difference in fiber lengths between the RAUs. ...
The performance of Time Division-Long Term Evolution (TD-LTE) Radio-over-Fiber (RoF) networks is investigated in this paper, in terms of downlink Physical Data Rate (PDR). It is shown that the accommodation of the extra propagation delay induced by the optical fiber links increases the protocol overheads and reduces the protocol's efficiency.
... A guard interval in the form of CP, which has to be sufficiently larger than the expected delay spread of the channel, is added between the OFDM symbols in order to eliminate Inter Symbol Interference (ISI) and preserve the orthogonality between the OFDM subcarriers [5], [6]. IEEE 802.16e [4], [5], defines four different values for the CP ratio G, the ratio of the guard period duration T g to the useful symbol time T b : 1/4, 1/8, 1/16, 1/32. ...
... Thus, the same signal will be received in multiple copies with a time delay difference due to the difference in optical fiber length used to connect the RAUs with the BS, which might cause ISI and data transmission degradation. As a result, in RoF networks, the CP could also be exploited to eliminate the ISI caused by the optical distribution network, although extended CP duration would mean greater energy consumption at the transmitter as well as bandwidth efficiency degradation [6]. ...
... We also calculate the theoretical maximum difference in fiber length between the RAUs that can be accommodated by each of the CP durations so that no "optical" multipath interference exists. Practically the guard time length has to be either 2-4 times the maximum anticipated delay-spread or kept to 25% of T b [6]. The authors of both [2] and [8] have used a guard time duration of 2 and 3 times, respectively, the propagation delay corresponding to the difference in fiber lengths between the RAUs. ...
This paper investigates the performance of the IEEE 802.16e Medium Access Control (MAC) in 802.16e Radio-over-Fiber (RoF) networks, in terms of MAC Data Rate (MDR). It is shown that the accommodation of the extra propagation delay induced by the optical fiber links increases the protocol overheads and reduces the protocol's efficiency.
