Using IEEE Standards for Wireless Body Area Networks. Similarities and Differences between the Previous IEEE 802.16.4 and the Current IEEE 802.15.6 Standard
Research Paper (postgraduate) 2015 5 Pages
Study of IEEE Standards for Wireless Body Area Network
Ronak U. Patel, RIT Student
Abstract— Body area network (Ban) is the most advanced technology in wireless communications and electronics. The recent BAN’s applications prove how this becoming more demanding to everybody. Some of these applications are medical applications, it is possible to implant, or wear, tiny health monitoring sensor nodes on the body so that the vital body parameters and the movements of the patient can be recorded and communicated to the medical facilities for further actions such as processing and diagnosis as well as it is also used in non-medical application areas such as entertainment, military. As said BAN has many applications and they have specific hardware and network requirements with low power consumption. It is also important for BANs are secure, protected and reliable. BANs have Specific requirements for the applications in terms of Range, Interference, Network density, Sensors number per network, In-body environment, Security/encryption, Quality of Services (QoS) and reliability, Support for different data rates, Compatibility with other PANs, Ultra low power consumption, Suitable sensors, Lifetime, Low cost, Low complexity and because of these all reasons we standardized BANs. To meet these requirements, Task group 6 was set up to introduce a new standard for Body Area Networks, and first, it is introduced in April, 2010. Since this is still an ongoing standard, before that, there are various existing and widely used wireless communication standards. Some commonly used standards are IEEE 802.11 (WLAN), IEEE 802.15 (WPAN), including IEEE 802.15.1 (Bluetooth), IEEE 802.15.4 (ZigBee), etc. In this paper, we will discuss IEEE 802.15.6 standards and point the similarities and differences with the previous IEEE 802.16.4 standards and try to discuss particular reasons why we developed a new standard and moved from IEEE 802.15.4 to IEEE 802.15.6 for WBAN.
Index Terms— Wireless body area networks, IEEE 802.15.4, IEEE802.15.6
As advance in electronics and computer science, there is an increase of using different types of sensors in our daily life and in future our most of the activities will include sensor networks. And particularly in healthcare industry the use of wireless sensor networks will be more. Much research has shown that it is possible to prevent diseases if it is detected in their early stages. This is possible through wireless body area networks (WBAN) they are like wearable monitoring systems that consists intelligent, low-power, sensors that are implanted in/on human with the capability of detecting and processing data and send it to the server device so that patients can do their normal activities instead of staying in hospital.
Because of the recent advances in WBAN, they are just not only used in medical and healthcare applications. They also been considered for sports, military and entertainment. So for all this application, we require particular standards with some specifications and it should be unique to standardize all WBAN applications. We have to more careful about standards because in this communication is going to happen in or on around the human body.
IEEE 802.15.6 is the recent standard which has been developed and presents a number of advantages when compared to other forms of wireless communications standards, and at the same time it has a wide range of applications which targets to improve human lives to a greater percentage. Mainly this standard target short range, low cost, minimum power usage of infrastructure and low complexity and above all this standard will utilize three aspects which include Medium Access Layer (MAC), Physical Layer (PHY) and Security. Before this standard we were using a IEEE802.15.4 standard for WBAN but they do not satisfy medical communication requirements mainly in terms of data rate, power consumption and bandwidth efficiency.
Our main purpose of this paper is to study WBAN and its particular requirements in terms of network and hardware, discuss the present and past standards that are used for WBAN and brief details of IEEE 802.15.6 standards. Another section of this paper includes brief study and comparison of IEEE 802.15.4 and IEEE 802.15.6 standards for WBAN and in the future, which problems to be expected in IEEE 802.15.6 standard.
II. KEY APPLICATIONS OF WBANS
According to IEEE 802.15.6 standard WBAN applications are mainly categorized into two categories that are medical applications and non-medical applications. As shown in Fig.1 includes major WBAN applications.
Medical applications include continuous real time monitoring of human attributes like blood pressure, body temperature and heart beat and send it to the remote server and take actions according to given directions. It is also used for people with disabilities to assist them to treat particular weakness using remote control medical devices.
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Fig. 1. WBAN applications
Non-medical applications includes real time streaming, emotion detection, gesture detection in 3D gaming, social networking and non-medical emergency, such as fire and gas detection It is also used in military for solder’s vital sign monitor and in sports for security purpose.
III. HISTORY OF THE WBAN STANDARDS
IEEE 802.15.6 is a current standard for WBAN but before that, various used wireless standards are WLAN (IEEE 802.11) and WPAN (IEEE 802.15.x) including Bluetooth and ZigBee. In order to satisfy requirements of different application in terms of data rate, power constraint, life time, latency, security, QoS etc. 
Besides all previous standards, IEEE 802.15.4 (WPAN) mainly ZigBee is best choice for WBANs because of their longer lifetime, low power requirements and their quick network joining time. All though, it has various advantages it does not satisfy communication requirements of networks because it’s close proximity to the human body tissues. So for all of this a unique model was required for successful implementation of WBAN for medical as well as non-medical applications.
Task group 6 (TG6) was established to design a new standard for Body Area Networks, we now called it IEEE 802.15.6. The first draft was released by this research group in April, 2010. And the approved version of IEEE 802.15.6 standard was modified in February 2012. The aim of this is to develop a standard for low power devices that can operate on, in or around human body to serve various medical and non-medical applications.
IV. REQUIREMENTS OF WBANS IN IEEE 802.15.6
The general requirements of IEEE 802.15.6 are as follows: [4, 6-10]
- WBANs should support data rate from 10 Kb/s to 10 Mb/s.
- Network setup time should be less than 3 seconds.
- Packet Error Rate (PER) should not be more than 10% for a 256-byte payload.
- Network should be capable of 256 devices/network
- Latency, less than 250 ms in non-medical and less than 125 ms for medical applications.
- Network density, it should support 10 random WBANs in 6m cube.
- All devices are capable of transmitting power at 0.1 mW.
- Specific Absorption Rate (SAR) complaint below 10dBm on surface.
- WBANs should be capable of communicating with other networks of different standards to receive information.
- It should have power saving mechanisms to operate in power constrained environment.
- It should have features like priority services, secure authentications and self-healing services.
- It should have minimum interference between transmission of various sensors on the same application as well as different applications on the same body and it should have reliable communication even when the network is not static.
- It should have long life time, particularly in body sensors.
- It should have low complexity and low cost.
A. PHY Layer Specification:
IEEE 802.15.6 standard has three physical layers (PHY) which incorporates Ultra wideband (UWB) Human Body Communications (HBC) and Narrowband (NB) layers. The selection of the PHY layer is based on the application. The main function of the PHY layer is to provide a procedure for transforming PSDU (Physical layer service data unit) into PPDU (Physical layer protocol data unit).
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Table 1. FREQUENCY BAND AND BANDWIDTH O F DIFFERENT PHY LAYERS OF IEEE 802.15.6 
Activation and deactivation of radio transceiver, Data transmission and reception and CCA (clear channel assessment) in existing channel is controlled by Narrowband layer. NB PHY uses differential binary phase-shift keying (DBPSK) and differential quadrature-phase shift keying (DQPSK) and differential 8-phase shift keying (D8PSK) modulation technology in addition MHz 420 using a Gaussian minimum shift keying (GMSK) technology.
The HBC PHY layer provides specification for Electrostatic Field Communication (EFC) that includes entire WBAN protocol such as modulation, packet structure, preamble/start frame delimiter. This has two recurrence groups in which it works, which are focused at 16 and 27 MHz and bears a data transfer capacity of 4 MHz
The UWB PHY layer provides higher data rates and throughput so it is used for communication between on-body devices as well as for communication between on-body and off- body devices. It works in two recurrence groups, that is high and low band, where every band is further isolated into directs whose attributes falls in accordance with a transmission capacity of 499.2 MHz, the low band has just three channels (1 to 3) where channel two has a focal recurrence of 3993.6 MHz and this recurrence must be there. On the other side the high band has seven channels (4 to 11) with channel seven as the focal (recurrence 7987.2 MHz is an unquestionable requirement for this situation.
B. MAC Layer Specification:
The MAC layer is responsible to control channel access, timing synchronization and user datagram transfer function. In IEEE 802.15.6 MAC layer channel is chunked into structures called super frames, which are bound by an equivalent length of beacon period. This is done by hub (Coordinator) which choose the guide period limits for super frames to enable device synchronization and network association. In general beacons are passed on at each beacon period unless super-frames are latent or limited by the regulations such as Medical Implant Communication Service (MICS) band. Because of this feature MAC layer provides three access modes that are: Beacon mode with beacon period super-frame boundaries, Non-beacon mode with super-frame boundaries and Non-beacon mode without super-frame boundaries all access modes are coordinated by the hub.
V. COMPARISON BETWEEN IEEE 802.15.6 AND OTHER STANDARDS
In this section first, in Table.2 we will compare the various specification of current WBAN standard with other standards and then specifically with WPAN (IEEE 802.15.4) standards.
In all other wireless standards the main problem was that they do not satisfy the data rate and power requirements of WBANs. Fig.2 shows that some of the other standards satisfy the speed requirement of IEEE 802.15.6 but they do not satisfy power requirements (< 10mW) in WBANs.
Table.2 Comparison between IEE 802.15.6 and other IEEE 802.15 standards
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VI. KEY DIFFERENCES BETWEEN IEEE 802.15.4 AND IEEE 802.15.6
Now we will address the general and technical requirements of IEEE 802.15.6 (WBAN) and compare it with IEEE 82.15.4 (WPAN/ZigBee).
A. Supported Applications:
WBANs mainly used in medical applications, but it also used in Consumer Electronics, Entertainment, Gaming, Social media, ambient intelligence and military. Whereas ZigBee mostly used in general applications like Home, Industrial & Plant automation, Lighting, Meter reading and many more.
WBANs are implanted in or on around body so for them operating space is up to 3m but they are connected to a remote server for data transmission for long range. ZigBee supports range from 10m to 100m.
C. Data Rate:
As Shown in Fig.2 WBANs supports wide range of data rates from sum Kbps up to 10Mbps in contrast ZigBee supports 20, 40 or 250 Kbps
D. Power Consumption:
WBANs is capable of transmitting at 0.01-1 mW in standby mode and up to 40 mW in full active mode. On the other hand, in ZigBee devices transmitter operated in 25-35 mW and receiver between 25-40 mW. (In 2.4GHz)
E. Network Size and Setup time:
The Latest WBANs supports up to 256 devices per network and takes up to 1 Sec time to setup network. Alternatively ZigBee supports huge network size up to 65k devices and setup time is typically 50 ms.
WBANs can communicate other devices like WLAN, WPAN, and Bluetooth and simultaneously collect information of 256 devices from different Bans. ZigBee can support multiple ZigBee devices belonging to different personal area networks.
G. Quality of Service:
WBANs gives guaranteed and reliable response with Bit Error Rate (BER) from 10- to 10- and Latency from 10ms - 250ms. It also supports battery saving mode, acknowledgments, in order delivery and asymmetric links. ZigBee does not provide guaranteed response even though it supports Acks.
WBAN provides Privacy, Secure Authentication, Message Integrity, Encryption, Application and Network Security. ZigBee uses 128 bit encryption and also provides App. And Network Security.
I. Target Frequency bands:
WBAN only supports Unlicensed and Medical approved bands, e.g. MICS, MEDS, ISM, and WMTS (Consumer Electronics applications confined to ISM bands.) as Shown in Fig.3 where ZigBee supports 868, 915 or 2400MHz bands.
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Fig.3 IEEE 802.15.6 frequency bands
Taken from http://www.mdpi.com/sensors/sensors-14-09153/ article_deploy/html/images/sensors-14-09153f6-1024.png
J. Safety and Bio-friendly:
WBAN meets regulation requirements for Specific Absorption Rate (0-10 dB) and HIPPA (Health Portability and Accountability Act) oppositely ZigBee doesn’t follow any safety regulation.
K. Medium Access Control and Routing:
WBAN has single Scalable, robust, reliable, low complexity MAC and they use simple and direct communication (Wearable devices) and indirect communication (Implanted devices) via wearable devices. Whereas ZigBee uses CSMA-CA protocol in medium and provide Multi-hop, Tree (Simple) and Mesh (Complex) Routing.
L. Modulation and signal Coding:
The transmission of binary data over the wireless medium, requires the data to undergo changes from analogue to digital modulation. The retrieval of binary data from the digital form of analogue signal requires conversion of the analogue signals into digital form. To accomplish this task, the IEE 802.15.6 and IEE 802.15.4 use different modulation techniques. Some of the common techniques used by IEE 802.15.4 are BPSK, OQPSK, ASK, DSSS, PSSS, PSK, and SS.
On the other hand, the IEEE 802.15.6 uses 64-QAM, OFDM, FSK, 8DPSK, and CCK. The 64-QAM technique used by IEEE 802.15.6 manages to map 6 data bits at the same time into every transmitted symbol. The mapping of the 6 data bits at the same time is also known as high order modulation and it is capable of providing a high spectral efficiency if and only if it is combined with OFDM.
M. Full Function Device VS. Reduced Function Device:
The IEEE 802.15.4 in the full function device (FFD) is applicable in any topology, and the network coordinating in all the topologies is possible. In contrast, in the full function device, the IEEE 802.15.6 is applicable in only specified topology, and network coordination is better as compared to IEEE 802.15.4 standards. The ability to talk to any device is possible with IEEE 802.15.4, however, the same case never applies to IEEE 802.15.6 since talking is limited to specified devices. In terms of reduced function device (RFD), IEEE 802.15.4 is limited to star topology while IEEE 802.15.6 has no such limitation and has the capability of usage in other remaining topologies. The IEEE 802.15.4 has no ability to become a network coordinator, on the other hand, IEEE 802.15.6 has the capability of becoming a coordinator. Talking is restricted to only a network coordinator in IEEE 802.15.4 and its implementation is simple. On the contrary, the IEEE 802.15.6 has the ability to talk to other coordinators apart from network coordinator, however, its implementation seems a bit cumbersome.
Other than this all, WBANs has features like Robustness, Fault tolerance, Synchronization, Reprogramming, Priority services and Ability to access devices remotely over IEEE 802.15.4.
VII. FUTURE CHALLENGES
The above discussion states that although IEEE 802.15.6 standards have vast advantages over other standards, but we can say it is on saturation level and we can face some issues in this standard like characteristics of sensor materials and electric circuit because sensors are implanted in/on the human body so we have to keep in mind some constraints and it should not harm to the body tissues. Power supply is also a challenging issue because we are using wireless networks so it is powered by batteries which may not be replaced frequently since it is installed in-body so we have to develop techniques to recharge batteries remotely. We may need to enhance our physical layer and network layer specification to provide energy efficient communication and improve QoS. Other than this Security, privacy and authentication is also a major issue because we are dealing with the medical data of the patient that can’t be tampered, it should be private and confidential to protect patient privacy.
In this study, we reviewed key aspect of Wireless Body Area Networks and its applications. We discussed current WBAN IEEE 802.15.6 standard in detail and give a review on previously used standards for it. Here we also made some comparison between IEEE 802.15.6 and IEE 802.15.4 and explained various advantages of WBAN over ZigBee and also detected some areas in which we can face some issues in the future. This paper can be used to get the basic concepts of IEEE 802.15.6 instead of reading whole standard.
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