Full length articleError probability model for IEEE 802.15.4 wireless communications in the presence of co-channel interference
Introduction
The standard IEEE 802.15.4 for Low-Rate Wireless Personal Area Networks (LR-WPAN) [1] is the most widely used as a base for implementation of Wireless Sensor Networks (WSN). This standard complies with basic principles of WSN, which include: low power, low complexity and low cost. The physical layer of the IEEE 802.15.4 standard defines channels in several frequency bands, where the unlicensed 2.4 GHz ISM (Industry, Science and Medicine) band is the most commonly used worldwide. IEEE 802.15.4 signals are affected by noise and various types of interferences when sent through a wireless channel, which can change the received signal in such a manner that it is decoded with some data errors. IEEE 802.15.4 devices use the Direct Sequence Spread Spectrum (DSSS) signal spreading technique to enable coexistence of IEEE 802.15.4 networks in an overcrowded ISM band. IEEE 802.11 WLAN channels in the ISM band are wider, and overlap several IEEE 802.15.4 channels, but use different modulation and different DSSS spreading sequences, and its influence is referred to as wideband interference. IEEE 802.15.1 Bluetooth networks in an ISM band use narrow frequency hopping channels and their influence on the IEEE 802.15.4 signal is considered as narrowband interference. The signal spreading technique in the IEEE 802.15.4 standard is used to improve resistance with such types of interferences. Co-Channel Interference (CCI) originates from collisions between IEEE 802.15.4 devices which perform simultaneous radio transmission. The IEEE 802.15.4 standard uses the CSMA/CA (Carrier Sense Medium Access with Collision Avoidance) channel access mechanism to prevent collisions between devices, however this mechanism does not provide protection from a hidden node problem, which is the primary source of CCI.
Existing simulation tools usually treat all noises from distinctive types of sources as one noise; despite this, they have a rather different effects on wireless transmission. Furthermore, most simulation tools consider the occurrence of CCI as the inevitable loss of transmitted packets. Papers [2], [3] claim that, in the case of CCI, the stronger information signal can be received without errors, using capture effect. In order to exploit this effect, there is a need for an appropriate mathematical model of IEEE 802.15.4 wireless transmission in the presence of CCI. In our work, we will present analytical error probability models for chip, bit, symbol and packet error probability of IEEE 802.15.4 wireless transmission in the presence of CCI.
The state-of-the-art papers in this field, as much as it is known, analyze error probability of IEEE 802.15.4 transmission in the presence of background noise and fading in [4], [5], [6], [7], [8]. Error probability in the presence of narrowband and wideband interference from other types of networks (IEEE 802.11 and IEEE 802.15.1) is analyzed in papers [9], [10], [11], [12], [13]. In addition, the IEEE 802.15.4 standard [1], in its Annex E, provides a bit error probability equation in the case of interference from coexisting IEEE 802.11 and IEEE 802.15.1 networks. These papers treat influences of these narrowband and wideband interference on error probability in the same way as background noise. As far as it is known, an exact analysis of error probability parameters for IEEE 802.15.4 wireless transmission in the presence of CCI from other IEEE 802.15.4 devices, which operate in the same channel, does not exist. The authors in papers [14], [15] like many others, treated the influence of IEEE 802.11 networks which operate in the same band as IEEE 802.15.4 networks as CCI, despite the fact that IEEE 802.11 networks use much wider channel bandwidth.
In our paper, we derived the accurate analytical models for chip, symbol, bit and packet error probability in the case of CCI and background noise by consideration of non-ideal features of the used spreading sequences. The developed error probability models could be used in network simulation tools to analyze the influence of CCI in simulation scenarios which include hidden nodes. Recent emergence of IoT paradigm, tends to interconnect household appliances which possess embedded computational capabilities. The latest surveys found that the IEEE 802.15.4 standard is most commonly used for realization of IoT applications [16]. IoT devices are often deployed in relatively dense topologies combined with intense data communication due to the transmission of large Internet packets over IEEE 802.15.4 radio. Therefore the occurrence of CCI in IoT networks is much more probable due to hidden node collisions. Thus, accurate error probability models in the case of CCI are vital for performance analysis of WSN and especially IoT networks based on the IEEE 802.15.4 standard.
Section snippets
Probability of co-channel interference
Co-channel interference can occur between multiple IEEE 802.15.4 devices which operate in the same radio channel when they attempt simultaneous radio transmission. The IEEE 802.15.4 standard uses the blind backoff CSMA/CA channel access mechanism in which the device checks the channel state prior to transmission. If it determines that the channel is idle, it can begin with packet transmission. Otherwise, if the device detects radio transmission of another device, it reattempts channel access
Error probability of IEEE 802.15.4 transmission with CCI
The physical layer of the IEEE 802.15.4 standard for the 2.4 GHz ISM band defines 16 channels with bandwidth of 2 MHz and data rate of 250 kbps. IEEE 802.15.4 packets can be up to 133 bytes long, 127 bytes for payload, with an additional 6 bytes reserved for synchronization header and packet length fields. Each byte of the packet which needs to be transmitted is mapped using two symbols. The four least significant bits (, , , ) from each byte are first mapped as one symbol while the
Numerical simulations and results
In order to verify the proposed analytical models for CCI we developed an independent MATLAB simulation model using Monte Carlo simulation model for IEEE 802.15.4 communication in the 2.4 GHz ISM band with CCI and AWGN. The numerical simulation model was composed from a transmitter, interferer and receiver implemented in compliance with the IEEE 802.15.4 standard, which communicates through an AWGN channel. The transmitter forms packets whose content is generated randomly by the pseudorandom
Experimental measurements and results
Measuring error probability parameters in the real communication system can be used for the evaluation of analytical and simulation results in the presence of CCI and AWGN. Packet error rate can be measured on commercially available IEEE 802.15.4 transceivers because the MAC (Medium Access Control) layer employs FCS (Frame Check Sequence) footer for checking the consistency of packets and finding packet errors. By analyzing the differences between the transmitted and received packets, besides
Conclusion
The research motivation of this paper was aimed at deriving an accurate analytical model for error probability parameters for IEEE 802.15.4 networks in the presence of CCI. Error probability models with influence of CCI are important for realistic simulations of MAC protocols for IEEE 802.15.4 networks because these networks are susceptible to hidden node collisions, which are the primary cause of CCI. We presented our simulated numerical results for the probability of occurrence of multiple
Acknowledgment
The work presented in this paper was funded by Grant TR32043 for the period 2011–2017, by the Ministry of Education and Science of the Republic of Serbia.
Uroš Pešović received the B.S. degree in Computer Science from University of Kragujevac, Serbia in 2006, M.S. degree from the University of Maribor, Slovenia in 2010 and Ph.D. degree at Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia in 2016. He is involved in research on wireless sensor networks in fields of modeling error probability and efficient medium access. He is currently employed at Faculty of Technical Sciences in Čačak, University of Kragujevac
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Uroš Pešović received the B.S. degree in Computer Science from University of Kragujevac, Serbia in 2006, M.S. degree from the University of Maribor, Slovenia in 2010 and Ph.D. degree at Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia in 2016. He is involved in research on wireless sensor networks in fields of modeling error probability and efficient medium access. He is currently employed at Faculty of Technical Sciences in Čačak, University of Kragujevac in Serbia as teaching assistant and researcher on project TR32043 financed by the Ministry of Education and Science of the Republic of Serbia.
Peter Planinšič received the B.S. Degree in 1979 and M.S. Degree in 1991 from University of Maribor, Slovenia and received Ph.D. at University of Maribor, Slovenia in 2000, all in electrical engineering. He is involved in research areas of signal processing and telecommunications. He is currently employed as associate professor at Faculty of Electrical Engineering and Computer Science, University of Maribor, Slovenia.