Dynamic adaptive frequency hopping for mutually interfering wireless personal area networks

A Wireless Personal Area Network (WPAN) provides wireless links among proximate devices,usually carried by an individual.As WPAN gains momentum in ubiquitous usage, the interference that collocated WPANs cause to each other, termed self-interference, becomes one of the major sources that degrade the communication performance of WPAN. This paper in roduces the Frequency Rolling (FR), a particular instance of frequency hopping (FH) that enables he collocated WPANs to cooperate and avoid the self-interference. The FR uses as input solely the observed packet error rate (PER) and it does not require any exchange of information among he collocated WPANs. The effect of the FR over a longer time in erval is hat the WPANs use he complete set of disposable channels in an implicit time-division and cooperative manner. The parameters of he FR are chosen such that a WPAN which uses FR never occupies the channels in the unlicensed spectrum more than what is permitted by the current regulation. We compare the goodput offered by FR to the goodput of the collocated piconets when conventional pseudorandom FH is used. Our simulation results show that FR has superior goodput performance. In addition, he design of FR is made robust owards the errors due to the channel noise. Some guidance for practical fault-toleran design and future extensions of FR are given. All hese features promote the great potential of FR as a coexistence mechanism for unlicensed operation.

Supporting multimedia traffic is one of the major challenges for the next generation of wireless personal area networks (WPANs). Especially, the IEEE 802.15.4 WPAN standards specify how to guarantee real-time traffic with a type of time division multiple access (TDMA), called the guaranteed time slots (GTS). The GTS mechanism has led many researchers to design techniques aiming to support various real-time applications within the delay jitter. Since the IEEE 802.15.4 standards can operate at low data rate up to 250Kbps, it is limited to guarantee real-time multimedia traffic except voice. The voice traffic has bidirectional characteristics and may go through the multihop in WPAN which can support short-range communications among electronic devices. In this paper, we introduce a virtual cut-through GTS allocation mechanism, namely VC-GTS allocation, for voice traffic in multihop IEEE 802.15.4 systems. The proposed scheme can support bidirectional voice traffic and delivery the traffic to the destination through multihop paths with the minimum end-to-end delay time. The most important thing is that our proposed scheme achieves low delay time and packet error rate without a complex allocation algorithm in multihop IEEE 802.15.4 networks. Our simulation results show that our new scheme outperforms the basic IEEE 802.15.4 GTS mechanism.

In this paper, an adaptive and self-organizing spectrum allocation policy for ad hoc femtocells in two-tier networks based on usage of random frequency hopping is presented. As femto- and macrocells normally share the same frequency resources, the proposed approach is able to minimize InterCell Interference (ICI) in an adaptive manner. Each femto- and macrocell user chooses random carrier frequencies for transmission corresponding to a given probability density function (pdf). If the level of interference reaches a certain limit, which is typically the case for femtocell edge users, the probability density function of the carrier frequencies is changed in a way that it is quasi-orthogonal to the one of the macrocell users nearby. The changeover point between different probability density functions is realized in a self-organizing manner regarding the detected level of interference. Hence, the approach is able to adjust the trade-off between spectral efficiency and introduced interference during operation. We present analytical models for the Signal-to-Interference-and-Noise-Ratio (SINR), the Bit Error Ratio (BER) and the required transmission power of Orthogonal Frequency Division Multiple Access (OFDMA) femtocells applying adaptive random frequency hopping. The mobile radio channel is characterized by non-frequency selective Rayleigh fading and all results are verified by simulations implemented in MATLAB. In order to evaluate the improvements, the results are compared to systems using centralized orthogonal planning, systems using neither centralized nor distributed planning, and systems using static random frequency hopping. The comparison shows that adaptive random frequency hopping is capable of reducing the BER by a factor of 15 and the transmission power of femtocells by 17 dBm compared to systems where the macrocell user transmits in the same subbands as the femtocell user.

Problem statement: In universal networking environments; two or more heterogeneous communication systems coexisting in a single place. Especially, Wireless Local Area Networks (WLANs) based on IEEE 802.11b specifications and Wireless Personal Area Networks (WPANs) based on IEEE 802.15.4 specifications need to coexist in the same Industrial, Science and Medial (ISM) band. If the WPAN communication coverage is expanded using a cluster-tree network topology, then the 802.15.4 network is more susceptible to interference from neighboring WLANs. Approach: In this study, we propose an adaptive transmission power aware cluster scheduling algorithm using multiple channels in a WPAN in the presence of WLAN interference. Results: The algorithm includes node identification, channel allocation, clustering and time scheduling. To evaluate the performance of the proposed algorithm, the performance metrics such as Bit error, Packet Error Rate (PER), Throughput, Average End-End Delay and Average Jitter is measured through Qualnet simulation. PER is calculated from bit error rate. The simulation results are compared with the conventional TDMA scheme. Conclusion/Recommendations: The measurement result shows that the proposed algorithm is effective in an IEEE 802.15.4 cluster-tree network in the presence of multiple IEEE 802.11 interferers.

Interference among different wireless devices operating in the same frequency band in a given region is always a problem. The prominent type of it is the interference between Wireless Local Area Network (WLAN) and Wireless Personal Area Network (WPAN) devices operating in the 2.4-GHz unlicensed band. Various techniques such as Adaptive Frequency Hopping (AFH) were proposed recently to deal with this interference. When wireless devices are deployed on plant-floors, the approach required to mitigate the interference can be slightly different so that the proposed techniques should be able to support data prioritisation in addition to managing the interference. This will allow the important data through even if the interference levels are higher than expected. For this to take place, channel assessment should be done first, to find out which channels are suffering interference, to what levels and how often. This aspect of channel assessment is considered here, for different combinations of interferers and power levels.

The authors propose an adaptive frequency hopping (AFH) algorithm, entitled robust adaptive frequency hopping (RAFH), for providing increased reliability of a wireless medical telemetry system (WMTS) under coexistence environment with non-medical devices. The conventional AFH scheme classifies channels into `good` or `bad` according to the threshold-based on`off decision by packet error rate (PER) measurement, and only uses good channels with a uniform hop probability. Unlike the conventional AFH scheme, RAFH is a novel technique, which solves a constrained entropy maximisation problem and assigns every channel a different hop probability as a decreasing function of the measured PER. The key novelty of RAFH over existing AFH schemes is that it reflects the relative channel condition by assigning non-uniform hop probabilities. By adopting constrained entropy maximisation, RAFH not only improves the average PER, but also reduces the PER fluctuation over time under a dynamic interference environment, both of which increase the reliability of WMTS. Through extensive simulation, we show that RAFH outperforms basic frequency hopping (FH) and the conventional AFH with respect to the PER under various scenarios of dynamic interference.

The use of chirp-managed lasers (CML) for the distribution of OFDM-UWB radio signals in long-reach fiber-to-the-home passive optical networks (LR-PONs) is a cost-effective solution to extend the coverage of these signals in future wireless personal area networks (WPAN). Through numerical simulation, this paper analyzes the feasibility of the distribution of OFDM-UWB radio signals in LR-PONs using CML. The performance degradation of the transmission of OFDM-UWB signals is assessed in terms of the bit error ratio (BER) and, for a minimum BER of 10−4, the CML-based transmission achieves an improvement of 11 km in the maximum transmission distance compared to the use of a directly modulated laser.

Wireless Personal Area Network Communications, an Application Overview

For WPAN (Wireless Personal Area Network) applications, a low-power low-noise IF (Intermediate-Frequency) circuit is proposed for GFSK (Gauss Frequency Shift Keying) low-IF receivers. The proposed IF system is realized by an all-analog architecture, which is composed of a couple of LAs (Limiting Amplifiers) and RSSIs (Received Signal Strength Indicators), a couple of BPFs (Band-Pass Filters), a FD (Frequency Detector), a LPF (Low-Pass Filter) and a slicer. The chip is implemented with HJTC 0.18-μm CMOS technology and measured under a data rate of 100 kb/s, a carrier frequency of 200 kHz and a modulation index of 1.0. The RSSI has a dynamic range of 51 dB with a logarithmic linearity error of less than ±1 dB. For 0.1% BER (Bit Error Ratio), the minimum input SNR (Signal-to-Noise Ratio) of the proposed IF circuit is 5 dB, and the input dynamic range of the whole IF circuit is 55.4 dB. When the input SNR is set at 6 dB, the proposed circuit can tolerate a frequency offset from −3% to +9.5%. The total power consumption of the proposed IF circuit is 5.65 mW ∼ 5.89 mW.

Uncompressed HD (high-definition) video delivery over wireless personal area networks (WPANs) is a challenging problem because of the limited bandwidth and variations in channel. The 60 GHz millimeter-wave (mmWave) band has recently drawn much interest because of the huge bandwidth that it can provide from 57-66 GHz unlicensed spectrum available worldwide. However, to date a system design supporting uncompressed HD video over WPAN is still lacking. In this paper, we develop, simulate, and evaluate an mmWave system for supporting uncompressed video streaming over wireless (UVoW). New features of the UVoW system incorporates: (i) UEP (unequal error protection) where different video bits (MSBs and LSBs) are protected differently, (ii) a multi-CRC to determine whether MSB or/and LSB portions are in error, (iii) UV-ARQ, uncompressed video retransmission protocol which allows the receiver to request only those portions of a video packet which have high importance. Simulations indicate that the UVoW system achieves significantly higher video quality than normal systems under various wireless channel conditions. This shows that UVoW is a promising wireless system supporting uncompressed HD video.

Wireless Personal Area Network Communications, an Application Overview

IEEE 802.22 wireless regional area network (WRAN) is an emerging cognitive radio-based system. One of the major challenges for WRANs is how to efficiently schedule both channel sensing and data transmission for multiple adjacent WRAN cells. This challenge is known as coexistence problem. In this paper, we propose four schemes that aim at reducing the coexistence-problem effect. These schemes are based on a well-known operation mode of IEEE 802.22, namely dynamic frequency hopping (DFH). The first and second schemes are based on using omni-directional antennas at the base stations (BSs), whereas the BSs in the other two schemes use directional antennas. The first scheme, coined fixed-scheduling DFH (FDFH), bases upon a fixed scheduling of working channels for adjacent WRAN cells. The second scheme, called cooperative DFH (CDFH), cooperatively selects working channels. The third scheme, namely sectoral DFH (SDFH), is proposed to reduce the coordination overhead of CDFH via dividing a WRAN cell into sectors to decrease the chances of collisions between adjacent cells. Finally, we integrate FDFH and SDFH into a new scheme, called fixed-scheduling sectoral DFH (FSDFH), which exploits the advantages of both schemes with no additional overhead. Computer simulations are used to demonstrate the performance gain of the proposed schemes.

Wireless systems based on WLAN (802.11), ZigBee (802.15.4) and Bluetooth (802.15.1) are continuously deployed in new applications covering consumer, industry or medical fields. Especially, Bluetooth is recommended by the Health-Care-Organization for medical applications as frequency hopping is considered as a robust scheme. However dealing with frequency-dynamic sources of interference in the 2.4GHz ISM band is important due to the increase of wireless devices. Adaptive frequency hopping (AFH) suggested by the Bluetooth standard and implemented in many of todays products identifies and avoids using bad channels. It is a good and established coexistence mechanism in the presence of frequency-static sources of interference such as WLANs when the 2.4GHz band is not crowded. However, AFH is facing problems in a crowded 2.4GHz band, especially when the interference is dynamic. We developed a cross-layer algorithm SAFH (Smooth Adaptive Frequency Hopping) that is inspired by entropy maximization and the conventional Bluetooth AFH. SAFH assigns usage probabilities to all channels based on an exponential smoothing filter for frame error rates to estimate and predict the channel conditions. The application layer can adapt SAFH by parameter settings in a cross-layer approach. SAFH achieves low average frame error rate and responds fast to changing channel conditions if required from the application. Simulative Evaluation in the presence of different types of interference (802.11b, 802.15.4 and 802.15.1) shows that our algorithm outperforms conventional frequency hopping and AFH. Additionally, SAFH works smoothly and stable exploiting frequency diversity compared to previous approaches like entropy-maximization based adaptive frequency hopping and Utility Based Adaptive Frequency Hopping (UBAFH).

Device-to-device (D2D) communication is such a paradigm that anticipated to play a cabalistic role for the next-generation cellular networks especially for the 5G cellular network as it promises to extend the network coverage and offload some traffics from the cellular transceiver’s side to the user devices’ side and it may operate in both licensed and unlicensed spectra simultaneously. D2D communication in the unlicensed spectrum may facilitate the purpose of D2D communication as the licensed spectrum almost possessed. Interference is the main drawback of the unlicensed spectrum. In this paper, we propose the request-to-send/clear-to-send (RTS/CTS) mechanism with the free-to-receive (FTR)-MNAV technique to improve the performance of the D2D communication in the unlicensed spectrum. Deployment of the carrier sense multiple access with collision avoidance (CSMA/CA) protocol can alleviate interference, but collisions occur due to the hidden node problem. The integration of the RTS/CTS mechanism with the CSMA/CA protocol can minimize the hidden node problem, but the blocking and false blocking problems are introduced. The proposed scheme can reduce the blocking and false blocking problems, which improves the performance of the D2D communication in the unlicensed spectrum where neighbor nodes maintain Multiple Network Allocation Vector (MNAV) to resolve the blocking problem and broadcast the FTR control packet to the respective neighbor nodes if the transmission is completed prior to the expiration of the timer or actual communication does not take place due to any reason, thus solving the false blocking problem and improving the performance of the D2D communication in the unlicensed spectrum.

<div class="section abstract"><div class="htmlview paragraph">Aviation industry is striving to leverage the technological advancements in connectivity, computation and data analytics. Scalable and robust connectivity enables futuristic applications like smart cabins, prognostic health management (PHM) and AI/ML based analytics for effective decision making leading to flight operational efficiency, optimized maintenance planning and aircraft downtime reduction. Wireless Sensor Networks (WSN) are gaining prominence on the aircraft for providing large scale connectivity solution that are essential for implementing various health monitoring applications like Structural Health Monitoring (SHM), Prognostic Health Management (PHM), etc. and control applications like smart lighting, smart seats, smart lavatory, etc. These applications help in improving passenger experience, flight operational efficiency, optimized maintenance planning and aircraft downtime reduction. Intra Aircraft WSNs (IAWSN) used for such applications are expected to provide robust and reliable communication performance. However, IAWSNs, when deployed, must co-exist with other wireless devices and networks based on Wi-Fi and Bluetooth technologies. Sharing of the ISM frequency band (2.4 GHz) among these networks makes the co-existence problem more challenging and has a significant impact on the Quality of Service (QoS) in terms of throughput, latency and Packet Error Rate (PER) of IAWSN. In addition, they are subjected to additional electromagnetic interference from other electronic and avionic systems onboard aircraft. There are various channel management, priority-based scheduling and time-sharing techniques that are deployed currently to address the co-existence problem. However, these methods perform a trade-off among one or more operational parameters like channel bandwidth, number of nodes per channel, throughput, latency, PER, etc. of IAWSN. Code Division Multiple Access (CDMA) technique is a proven one in cellular networks for providing reliable interference free communication performance especially in large scale networks. This paper evaluates the feasibility of deploying CDMA for IEEE 802.15.4 based IAWSN onboard aircraft. A CDMA based communication schema is proposed and simulated for IAWSN operating as per IEEE 802.15.4 protocol. The communication performance of the CDMA based IAWSN is evaluated in comparison with the performance of a standard IEEE 802.15.4 protocol implementation in the presence of interference from the co-nodes of the IAWSN and Wi-Fi devices by analyzing the QoS parameters like signal to noise ratio (SNR), operational bandwidth, Bit-Error Rate (BER) and Process Gain through simulation. Simulations results are evaluated against the desired performance level for a reference use case application. Improvement opportunities are identified and areas for future research are proposed.</div></div>