Piconet construction and restructuring mechanisms for interference avoiding in bluetooth PANs

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Abstract

Bluetooth and IEEE 802.11 (Wi-Fi) are two of the most popular communication standards that define physical and MAC layers for wireless transmissions and operate on 2.4 GHz industrial scientific medical (ISM) band. To avoid the rich interference existed in ISM band, Bluetooth adopts a time-slotted frequency-hopping spread-spectrum scheme, preventing the Bluetooth device communication from being interfered for a long time on specific channel. However, the coexistence of Bluetooth and Wi-Fi in the neighborhood degrades the performance of both networks because the two wireless technologies cannot negotiate with each other. To improve the throughput of a given piconet, this paper presents two interference aware approaches. First, an interference aware piconet establishment mechanism, called IAPE, is proposed to consider the frequencies occupied by Wi-Fi and then minimize the interference from Wi-Fi transmissions, when Bluetooth and Wi-Fi coexist in the same space. To further improve the throughput of the constructed piconet, an interference aware piconet restructuring mechanism, called IAPR, is proposed. Performance study reveals that the proposed IAPE and IAPR approaches further reduce the interference between Bluetooth and Wi-Fi and thereby save the energy of Bluetooth device, improving the throughput of Bluetooth personal area networks (PANs).

Introduction

Bluetooth is a wireless technology, characterized by low power, low-cost, and short-range and operated on 2.4 GHz industrial scientific medical (ISM) band (The Bluetooth Specification.). Bluetooth has been widely embedded in a variety of electronic devices such as printers, mobile phones, laptops, home video and audio systems, as well as sphygmomanometers, supporting short-range wireless communications (Wang and Iqbal 2006; Abdullah and Poh, 2011). To avoid the rich interference existed in ISM band, it adopts a time-slotted frequency-hopping spread-spectrum scheme with a forward error correction (FEC) coding technique. The Bluetooth signal occupies 1 MHz bandwidth and changes center frequency (or hops) deterministically at a rate of 1600 Hz. Bluetooth hops over 79 center frequencies, equally spaced between 2.402 GHz and 2.480 GHz (Ophir et al., 2004; Gummadi et al., 2007). A piconet is the smallest network element that consists of a master device and slave devices (up to seven). Each piconet has its own hopping sequence that determines the communication channel in each time slot. In a piconet, the master and slave devices play the sender role and transmit packets in the even and odd slots, respectively. The transmission rate reaches up to 1 Mbps while the transmission range generally ranges from 10 m to 100 m, depending on the transmission power (Lee et al., 2007).

In the Bluetooth technology, interference from the other Bluetooth devices has been minimized because each piconet uses its own pseudo-random frequency-hopping pattern. However, several wireless technologies also share the ISM band, including Wi-Fi, ZigBee and others. In particular, the coexistence of Bluetooth and Wi-Fi degrades the network performance because the two wireless technologies cannot negotiate with each other. A single active Wi-Fi network causes the heavy interference on 37% of the Bluetooth channels (Lavric et al., 2012). Therefore, an open question in Bluetooth is how to avoid interference conflicts among devices, which try to simultaneously access a Bluetooth personal area network (PAN) or Wi-Fi network.

Previous work (Jeon et al., 2013) proposed an approach to avoid the in-device interference when Wi-Fi and Bluetooth radios coexisted simultaneously in the same device. In (Jeon et al., 2013), a canceler was introduced in the circuit to prevent the interference. However, study (Jeon et al., 2013) did not take the interference into consideration when the Bluetooth and Wi-Fi devices had coexisted in different devices.

Heterogeneous interference, such as Wi-Fi and Bluetooth coexistence, had various characteristics and properties (Lakshminarayanan et al., 2011). In order to reduce the interference, Baccour et al. (2012) proposed a mechanism based on the estimation of radio link quality to reduce the heterogeneous interference in wireless sensor networks (WSNs). The coexistence problems could be detected by the link quality estimator. However, the link quality estimation needed to send a considerable amount of control messages to make a decizion whether or not the interference exists. This raized many overheads, leading to the poor performance regarding the throughput.

To mitigate the phenomenon of the co-channel interference in the Bluetooth piconet, studies (Yoon et al., 2010; Lee et al., 2012) proposed approaches to check whether or not the next channel for the Bluetooth frequency hopping was occupied by the other signals. Lee et al. (2012) proposed a mechanism that periodically detected busy channels subject to the WLAN interference. The proposed mechanism evaluated the packet error rate and the interference signal detection rate before sending packets. However, this approach needed to periodically check every channel, leading to the considerable energy consumption. In addition, the scheme did not deal with the packet retransmission problem caused by the WLAN interference, further increasing the time and energy costs of packet retransmissions.

There have been many works on the Bluetooth role switch, but they are tending to propose a role switch formation protocols for constructing a proper scatternet. Study (Chang and Chang, 2006) can remove unnecessary bridges and the piconet using role witch to improve the packet error rate and reduce the average length. Study (Bakhsh et al., 2012) presents a flexible relay selection technique to reduce unnecessary relays. However, they didn’t consider to how to restructure a piconet dynamically when the master of Bluetooth piconet suffers the interference from Wi-Fi devices.

Study (Chiasserini and Rao, 2002) proposed two coexistence mechanisms, including V-OLA and D-OLA in the presence of a Bluetooth voice link and Bluetooth data link, respectively. In the V-OLA mechanism, whenever a 802.11 station is ready to transmit, it detects weather or not the channel is idle. If it is the case, the 802.11 station expects for a time period that there is no BT transmission and transmits a data packet within the expected time period. Conversely, if the channel is occupied by an interfering signal, the WLAN station can either (i) send a packet with a 500 bytes payload (Shortened Transmission (ST) mode) or (ii) refrain from transmitting (Postponed Transmission (PT) mode). In the D-OLA mechanism, a BT device can identify the frequency channels that are occupied. According to the D-OLA algorithm, if enough data are buffered at the master for the intended slave, the master schedules a multi-slot packet instead of a single-slot packet, aiming to skip the channels that are occupied by WLAN. The scheduling algorithm could also let the master (slave) refrain from transmitting in the time slot corresponding to a frequency that hops on the 802.11 band whenever there are not enough data in the buffer at the master. Though the proposed V-OLA and D-LOA mechanisms can avoid the collizion occurrence, the throughput and packet delay can be further improved. For example, the D-LOA will not allow the master to transmit data to slave at the next time slot if the working channel of hopping sequence is busy at the next time slot. However, our mechanism can utilize the next time slot to transmit data if the role of master has been changed to the slave. As a result, the packet delay and throughput can be improved. The following compares the proposed mechanism and the mechanisms proposed in (Chiasserini and Rao, 2002). First of all, in the connection process, the proposed mechanism IAPE tries to scan the channels that are occupied by 802.11. The constructed piconet will skip these channels in the hopping sequence. Therefore, no further detection is needed whether the piconet has been constructed. Hence, all time slots can be used for transmitting data, reducing the delay and improving the throughput. Second, the proposed mechanism IAPR actively reconstructs the piconet and the device that can minimize the transmission delay and maximal throughput will be invited to be the new master when the retransmission rate reaches the threshold. The proposed mechanism dynamically changes the piconet structure and thus can be further applied to the mobile network.

This paper presents a novel Bluetooth network construction mechanism that explores appropriate channels during link construction and reconstructs the piconet topology during data transmission for Bluetooth network, aiming at minimizing the interference between Bluetooth and Wi-Fi when they coexist in the same space. The contributions of this paper are itemized as follows:

  • (1)

    Avoiding the interference during Bluetooth link construction.

    The proposed interference aware piconet establishment (IAPE) mechanism constructs an efficient Bluetooth link by exploring the appropriate channels such that the hopping sequence skips the channels occupied by Wi-Fi.

  • (2)

    Reducing the network overheads raized by packet transmissions.

    This paper proposes an interference aware piconet restructuring mechanism (IAPR), which applies the role switching operations to restructure a new piconet. The reconstructed Bluetooth network reduces the phenomenon of packet retransmission and hence substantially reduces the network overheads.

  • (3)

    Reducing the energy consumption and the transmission delay for Bluetooth networks.

The time and energy costs of packet retransmissions are improved because of the lower collizion rate achieved by the proposed scheme. Hence the energy consumptions of Bluetooth devices can be saved.

The remaining part of this paper is organized as follows. Section II illustrates the network environment and formulates the problem investigated in this paper while Sections III and IV elaborate the proposed IAPE and IAPR mechanisms, respectively. Section V verifies the performance of the proposed mechanisms by MATLAB simulation. Finally, Section VI offers a conclusion.

Section snippets

Network environment and problem statement

To achieve the readability, Table 1 lists a set of notations that are used in this paper.

Interference Aware Piconet Establishment (IAPE) mechanism

This section presents the proposed novel Bluetooth connection protocol. In Bluetooth networks, a piconet is the basic networking unit. Bluetooth and Wi-Fi technologies share the same unlicensed ISM band in a piconet. As shown in Fig. 1, in a piconet, a master device and slave devices (up to seven) hop over 79 center channels, which are equally spaced between 2.402 GHz and 2.480 GHz, occupy the non-overlapped 1 MHz bandwidth. Similar to the Bluetooth standard, the Wi-Fi standard also operates on

Interference Aware Piconet Restructuring (IAPR) mechanism

In a Bluetooth network, a piconet consists of a master and at most seven slaves. Each slave can only exchange data with the master in a piconet where the slave-to-slave direct communication is not allowed. When the master is suffering the interference, the performance of a piconet will be highly impacted. This proposed interference aware piconet restructuring (IAPR) mechanism aims to apply the role switching operation to cope with the interference problem. Role switching operation enables a

Performance evaluation

This section investigates the performance evaluation of the Original and the proposed IAPR approaches by using MATLAB Simulink, where Original approach represents the Bluetooth Standard (The Bluetooth Specification.). The environment is set as follows. The size of service region is set by 60×60 m2. Recall that the notation Rθ denotes the threshold for executing the proposed IAPR approaches. Herein, the value of Rθ is set by 5 retransmissions. Assume that the flow data volume of each Bluetooth

Conclusion

This paper presents novel link connection and topology restructuring mechanisms, called IAPE and IAPR, respectively, for Bluetooth personal area networks (PANs). The proposed IAPE helps a pair of master and slave devices constructing an efficient link by excluding the inappropriate channels in their hopping sequences. In addition, an IAPR mechanism is proposed to restructure the topology of a piconet by applying role switching operations such that the new piconet can reduce not only the number

Acknowledgment

The paper is supported by National Natural Science Foundation of China (Grant no. 61472057), “Internet of things specialty” of Anhui Province (No. 2014tszy031), Chuzhou University Project (Nos. 2015GH08 and 2014KJ04), the Key Project of Anhui University Science Research (KJ2015A190) and the Technology R & D Program of Anhui Province of China (1501b042212).

References (17)

  • M.F.L. Abdullah et al.

    Mobile robot temperature sensing application via Bluetooth

    Int. J. Smart Home

    (2011)
  • N. Baccour et al.

    Radio link quality estimation in wireless sensor networks: a survey

    ACM Trans. Sens. Netw.

    (2012)
  • Bakhsh, S.T., Hasbullah, H., Tahir, S., et al., 2012. A Flexible Relay Selection Technique for Bluetooth Scatternet....
  • Balani, R., 2007. Energy consumption analysis for Bluetooth, Wi-Fi and cellular networks. Networked & Embedded Systems...
  • C.Y. Chang et al.

    Adaptive role switching protocol for improving scatternet performance in bluetooth radio networks

    IEEE Trans. Consum. Electron.

    (2006)
  • Chiasserini, C.F., Rao, R.R., 2002. Coexistence mechanisms for interference mitigation between IEEE 802.11 WLANs and...
  • Golmie, N., Chevrollier, N., ElBakkouri, I., 2001. Interference aware Bluetooth packet scheduling. In: Global...
  • R. Gummadi et al.

    Understanding and mitigating the impact of RF interference on 802.11 networks

    ACM SIGCOMM Comput. Commun. Rev.

    (2007)
There are more references available in the full text version of this article.

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