| 6Lo Working Group | MS. Akbar |
| Internet-Draft | Bournemouth University |
| Intended status: Informational | R. Bin Rais |
| Expires: December 15, 2017 | Ajman University |
| AR. Sangi | |
| Individual Contributor | |
| M. Zhang | |
| Huawei Technologies | |
| C. Perkins | |
| Futurewei | |
| June 13, 2017 |
Transmission of IPv6 Packets over Wireless Body Area Networks (WBANs)
draft-sajjad-6lo-wban-00
Wireless Body Area Networks (WBANs) intend to facilitate use cases related to medical field. IEEE 802.15.6 defines PHY and MAC layer and is designed to deal with better penetration through the human tissue without creating any damage to human tissues with the approved MICS (Medical Implant Communication Service) band by USA Federal Communications Commission (FCC). Devices in WBANs conform to this IEEE standard.
This specification defines details to enable transmission of IPv6 packets, method of forming link-local and statelessly autoconfigured IPv6 addresses on WBANs.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 15, 2017.
Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Wireless Body Area Networks (WBANs) are comprised of devices that conform to the [IEEE802.15.6], standard by the IEEE. IEEE 802.15.6 provides specification for the MAC layer to access the channel. The coordinator divides the channel into superframe time structures to allocate resources [SURVEY-WBAN] [MAC-WBAN]. Superframes are bounded by equal length beacons through the coordinator. Usually beacons are sent at beacon periods except inactive superframes or limited by regulation. This standard works under following three channel access modes.
Task group for 802.15.6 was established by IEEE in November 2007 for standardisation of WBANs and it was approved in 2012. This standard works in and around human body and focus on operating at lower frequencies and short range. The focus of this standard is to design a communication standard for MAC and physical layer to support different applications, namely, medical and no-medical applications. Medical applications refer to collection of vital information in real time (monitoring) for diagnoses and treatment of various diseases with help of different sensors (accelerometer, temperature, BP and EMG etc.). It defines a MAC layer that can operate with three different PHY layers i.e. human body communication (HBC), ultra-wideband (UWB) and Narrowband (NB). IEEE 802.15.6 provides specification for MAC layer to access the channel. The coordinator divides the channel into superframe time structures to allocate resources. Superframes are bounded by equal length beacons through coordinator. The purpose of the draft is to highlight the need of IEEE 802.15.6 for WBASNs and its integration issues while connecting it with IPv6 network. The use cases are provided to elaborate the scenarios with implantable and wearable biomedical sensors. 6lowpan provides IPv6 connectivity for IEEE 802.15.4; however, it will not work with IEEE 802.15.6 due to the difference in frame format in terms of size and composition.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
In the hospital environment, several levels of patient monitoring services are required as different patients needs different monitoring services e.g., a patient in Intensive Care Unit (ICU) requires high prioritized periodic data services with limited delay and high throughput than the patient in a normal ward. Usually, a patient is equipped with multiple sensors that measure vital signals like heart activity, muscle movements, blood pressure, body oxygen level and brain stimulation via integrated sensors i.e., (Electrocardiography), BP (Blood Pressure) monitor, EMG (Electromyography), pulse oximeter and EEG (Electroencephalography) etc. These sensors are categorized as wearable and implantable sensors, hence we are assuming that equipped sensors are mixture of wearable and implantable sensors which creates restriction to use IEEE 802.15.6 as it is designed to deal with better penetration through the human tissue without creating any damage to human tissues with the approved MICS band by USA Federal Communications Commission (FCC). In a hospital use case scenario, the initial data generated by numerous biomedical sensor nodes is collected by a central coordinator.
In this case, Table 3 presents the summary of traffic patterns for different biomedical sensor nodes attached to human body with data generation rate, required data rate from channel and QoS requirements.
| Sensor Nodes | Data Generation Interval | Required Data Rate (Kbps) | Delay Requirement | Power Consumption | Reliability Requirement |
|---|---|---|---|---|---|
| ECG | 4 ms | 34 | <125ms | Low | High |
| EMG | 6 ms | 19.6 | <125ms | Low | High |
| EEG | 4 ms | 19.6 | <125ms | Low | High |
| SpO2 (Pulse Oximeter) | 10 ms | 13.2 | <250ms | Low | Medium |
| BP | 10 ms | 13.2 | <250ms | Medium | Medium |
| Respiration | 40 ms | 3.2 | <250ms | Medium | Medium |
| Skin temperature | 60 s | 2.27 | <250ms | Low | Medium |
| Glucose sensor | 250 s | 0.528 | <250ms | Medium | Medium |
For a chronic disease patient, the formal procedure of routine visits is required to monitor the progress, development of complications or relapse of the disease. The questions like what, how and when to monitor are really crucial for disease treatment. In this context, various biosensors can be used for monitoring the patient's physiological conditions which brings relevant information on a regular basis. Appendix A and B shows patient monitoring use case scenario for WBAN.
The fast growth in the elderly population will produce a considerable shortage of healthcare experts in the near future. WBAN delivers a highly cost effective solution to monitor the physiological parameters of the elderly persons by seamless integration of their daily routine activities. Moreover, the physician can monitor the health conditions of an elderly person remotely by the courtesy of WBANs.
Based on the characteristics defined in the overview section, the following sections elaborate on the main problems with IP for WBANs.
The requirement for IPv6 connectivity within WBANs is driven by the following:
However, given the limited packet size, headers for IPv6 and layers above must be compressed whenever possible.
Applications within WBANs are expected to originate small packets. Adding all layers for IP connectivity should still allow transmission in one frame, without incurring excessive fragmentation and reassembly. Furthermore, protocols must be designed or chosen so that the individual "control/protocol packets" fit within a single 802.15.6 frame. Along these lines, IPv6's requirement of sub-IP reassembly may pose challenges for low-end WBANs healthcare devices that do not have enough RAM or storage for a 1280-octet packet [RFC2460].
The IEEE 802.15.6 working group has considered WBANs to operate in either a one-hop or two-hop star topology with the node in the centre of the star being placed on a location like the waist. Two feasible types of data transmission exist in the one-hop star topology: transmission from the device to the coordinator and transmission from the coordinator to the device. The communication methods that exist in the star topology are beacon mode and non-beacon mode. In a two-hop start WBAN, a relay-capable node may be used to exchange data frames between a node and the hub.
This is a standard for short-range, wireless communication in the vicinity of, or inside, a human body (but not limited to humans). It uses existing industrial scientific medical (ISM) bands as well as frequency bands approved by national medical and/or regulatory authorities. Support for quality of service (QoS), extremely low power, and data rates from 10Kbps to 10 Mbps is required while simultaneously complying with strict non-interference guidelines where needed. The Table 1 shows a comparison of WBAN and other available technologies in terms of data rate and power consumption.
| Standard | Provided data rate | Power requirement | Battery lifetime |
|---|---|---|---|
| 802.11 ac (WiFi) | 700 Mbps | 100 mW - 1000 mW | Hours - days |
| Bluetooth | 1Mbps - 10 Mbps | 4 mW - 100 mW | Days - weeks |
| Wibree | 600 Kbps maximum | 2 mW - 10 mW | Weeks - months |
| ZigBee | 250 Kbps | 3 mW - 10 mW | Weeks - months |
| 802.15.4 | 250 Kbps maximum | 3 mW - 10 mW | Weeks - months |
| 802.15.6 | 1Kbps - 10 Mbps | 0.1 mW - 2 mW | Months - years |
The purpose of this document is to provide an international standard for a short-range (i.e., about human body range), low power, and highly reliable wireless communication for use in close proximity to, or inside, a human body. Data rates, typically up to 10Mbps, can be offered to satisfy an evolutionary set of entertainment and healthcare services. Current personal area networks (PANs) do not meet the medical (proximity to human tissue) and relevant communication regulations for some application environments. They also do not support the combination of reliability, QoS, low power, data rate, and non-interference required to broadly address the breadth of body area network (BAN) applications.
All nodes and hubs (coordinator in 802.15.4) are to be organized into logical sets, referred to as body area networks (BANs) in this specification, and coordinated by their respective hubs for medium access and power management as illustrated in Table 1. There is to be one and only one hub in a BAN, whereas the number of nodes in a BAN is to range from zero to mMaxBANSize. In a one-hop star BAN [SURVEY-WBAN][RFC7326], frame exchanges are to occur directly between nodes and the hub of the BAN. In a two-hop extended star BAN, the hub and a node are to exchange frames optionally via a relay-capable node. Some of the characteristics of WBANs are as follows:
Figure 1 shows the general MAC frame format consisting of a 56-bit header, variable length frame body, and 18-bit FrameCheck Sequence (FCS). The maximum length of the frame body is 255 octets. The MAC header further consists of 32-bit frame control, 8-bit recipient Identification (ID), 8-bit sender ID, and 8-bit WBAN ID fields. The frame control field carries control information including the type of frame, that is, beacon, acknowledgement, or other control frames. The recipient and sender ID fields contain the address information of the recipient and the sender of the data frame, respectively. The WBAN ID contains information on the WBAN in which the transmission is active. The first 8-bit field in the MAC frame body carries message freshness information required for nonce construction and replay detection. The frame payload field carries data frames, and the last 32-bit Message Integrity Code (MIC) carries information about the authenticity and integrity of the frame.
Octets 7 0-255 2
+--------+------------------+--------+
| MAC | MAC frame body | |
| header |Variable length: | FCS |
| | 0-255 bytes | |
+--------+------------------+--------+
<--MHR--><--------X--------><---FTR-->
/ \
/ \
/ \
+---------+------------+-------------+--------------+
| Frame | Recipitent | Sender | Ban |
| control | ID | ID | ID |
+---------+------------+-------------+--------------+
Octets <--------><-----------><------------><-------------->
Figure 1: The general MAC frame format of IEEE 802.15.6
The USA Federal Communications Commission (FCC) and communication authorities of other countries have allocated the MICS band at 402-405 MHz with 300 KHz channels to enable wireless communication with implanted medical devices [[[REFERENCE TO BE ADDED]]]. This leads to better penetration through the human tissue compared to higher frequencies, high level of mobility, comfort and better patient care in implant to implant (S1), implant to body surface (S2) and implant to external (S3) scenarios. Additionally, the 402-405 MHz frequencies offers conducive propagation characteristics for the transmission of radio signals in the human body and do not cause severe interference for other radio operations in the same band. In fact, the MICs band is an unlicensed, ultra-low power, mobile radio service for transmitting data to support therapeutic or diagnostic operation related to implant medical devices and is internationally available. It is specifically chosen to provide low-power, small size, fast data transfer as well as a long communication range [SURVEY-WBAN][MAC-WBAN]. The frequency range of the MICS band allows high-level integration with the radio frequency IC (RFIC) technology, which leads to miniaturization and low power consumption. The PHY layer of IEEE 802.15.6 is responsible for the following tasks: activation and deactivation of the radio transceiver, Clear channel assessment (CCA) within the current channel and data transmission and reception. The choice of the physical layer depends on the target application: medical/non-medical, in, on and off-body. The PHY layer provides a procedure for transforming a physical layer service data unit (PSDU) into a physical layer protocol data unit (PPDU). IEEE 802.15.6 has specified three different physical layers: Human Body Communication (HBC), Narrow Band (NB) and Ultra-Wide Band (UWB). Various frequency bands are supported and shown in Table 2.
| Communication | Frequency | Bandwidth |
|---|---|---|
| HBC | 16 MHz | 4 MHz |
| HBC | 27 MHz | 4 MHz |
| NB | 402-405 MHz | 300 KHz |
| NB | 420-450 MHz | 300 KHz |
| NB | 863-870 MHz | 400 KHz |
| NB | 902-928 MHz | 500 KHz |
| NB | 956-956 MHz | 400 KHz |
| NB | 2360-2400 MHz | 1 MHz |
| NB | 2400-2438.5 MHz | 1 MHz |
| UWB | 13.2-4.7 GHz | 499 MHz |
| UWB | 6.2-10.3 GHz | 499 MHz |
o Beacon Mode with Beacon Period Superframe Boundaries:
Beacons are sent at beacon periods by the coordinator and the superframe structure is managed by the coordinator by using beacon frames. The Physical Protocol Data Unit (PPDU) frame of Narrowband (NB) consists of a PHY Service Data Unit (PSDU) and Physical Layer Convergence Procedure (PLCP). PLCP preamble supports the receiver for synchronization process and considers as first module being send at given symbol rate. PLCP header sends decoding information for the receiver and it is transmitted after PLCP preamble. PSDU is last module of PPDU and consists of MAC header, Frame Check Sequence (FCS) and MAC frame body. PSDU is transmitted after PLCP with help of available frequency band with specific data rates. Different modulations schemes can be used with NB, namely, Differential Binary Phase-shift Keying (DBPSK), Differential Quadrature Phase-shift Keying (DQPSK) and Differential 8-Phase-shift Keying (D8PSK). NB uses seven frequency bands and operates under different data rates and modulation schemes. Medical Implant Communication Service (MICS) is the first licensed band of NB and used for implant communication with range of 402-405 MHz in most countries. Lower frequencies possess less attenuation and shadowing effect from body. Wireless Telemetry Medical Services (WMTS) is another license band and used for telemetry services. Although, Industrial, Scientific and Medical (ISM) band is free worldwide but it generates high probability of interference for IEEE 802.15.4 and IEEE 802.15.6 devices and considered as 7th license-free band. The 6th band (2360-2400 MHz) is used for medical devices instead of ISM band and offers less interference.
The superframe structure consists of several phases: exclusive access phase 1 (EAP 1), random access phase 1 (RAP1), type I/II phase, an EAP 2, RAP 2 and contention access phase (CAP). CSMA/CA or slotted Aloha is used by EAPs, RAPs and CAPs. For emergency services and high priority data, the EAP 1 and EAP 2 are used, whereas, CAP, RAP 1 and RAP 2 are used for regular data traffic. Type I/II are used for bi-link allocation intervals, up-link and down-link allocation intervals and delay bi-link intervals. For resource allocation, the type I/II polling is used.
A node's backoff counter value is set to a random integer number in the range [1,CW (Contention Window)], where CW (default value is CWmin) belongs to CWmin and CWmax which is dependent on user priority. When the algorithm starts, node begins counter decrement by one for every idle CSMA/CA slot duration (slot duration is equal to Pcsma/CA slot length). A node considers a CSMA/CA slot idle if the channel has been idle between start of slot and pCCATime. When the backoff counter reaches zero, the node transmits the data frame. In case the channel is busy because of some other frame transmission, then node locks its backoff counter until the channel gets idle. The value of CW get double in case of even number of failures until it reaches CWmax [CHALLENGES-WBAN] [RFC7548].
o Beacon Mode with Superframe Boundaries:
For this mode, the coordinator provides an unscheduled polled allocation and each node establishes its own schedule. Different access mechanisms are used in superframe phases: schedule access (connection oriented and contention-free access), improvised and unscheduled access (connectionless and contention free access) and random access (CSMA/CA or slotted Aloha based).
o Beacon Mode without Superframe Boundaries:
In this channel access mode, beacons are not transmitted and channel is assigned by using polling mechanism.
This draft intend to standardize IEEE 802.15.6 for WBANs, specifically for implantable and wearable sensors. By standardizing means that integration of frame format need to be done i.e., how the IEEE 802.15.6 frame format will communicate with IPv6? How 6LoWPAN can accommodate this different frame format? The purpose of the mentioned use cases is to highlight the importance of the standard.
The 6LoWPAN is used to provide integration between IEEE 802.15.4 and IPv6. The details are mentioned in [RFC7548]. The 6LoWPAN concept originated with the purpose of connectivity of internet protocol with low-power smaller devices so they could claim to be part of Internet of Things (IoT) Networks.
The 6LoWPAN group has defined encapsulation and header compression mechanisms that allow ipv6 packets to be sent and received over IEEE 802.15.4 based networks, similarly the draft intent to define these mechanisms for IEEE 802.15.6. The 6LoWPAN can not be used with IEEE 802.15.6 due to frame size differences of IEEE 802.15.4 and IEEE 802.15.6.
[TBD]
IPv6 over WBAN's applications often require confidentiality and integrity protection. This can be provided at the application, transport, network, and/or at the link.
[TBD]
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC7548] | Ersue, M., Romascanu, D., Schoenwaelder, J. and A. Sehgal, "Management of Networks with Constrained Devices: Use Cases", RFC 7548, DOI 10.17487/RFC7548, May 2015. |
| [RFC7326] | Parello, J., Claise, B., Schoening, B. and J. Quittek, "Energy Management Framework", RFC 7326, DOI 10.17487/RFC7326, September 2014. |
| [RFC2460] | Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, December 1998. |
| [RFC4944] | Montenegro, G., Kushalnagar, N., Hui, J. and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007. |
Refer following diagram:
########
# @ EEG #
## | @ # Hearing
# | | #
# | |#
# | #|
##### | |## ###
# | | @ ## Motion Sensor
Positioning# @ | / / #
# \ |ECG / / #
# \ | @ | / #
# \ | / / / #
# ## \ |/ // ## #
# ## \ ||// ## #
# # # \ |||| # # @ # BP
# # # \|||| # # / ##
# ## # |||| # #/ ##
SPO2# @ ## # Coordinator # /## #
# \ ## ## +-+ / ## ##
# ------+--------| |-------/ # # #
## ## # +-+ ## # ##
## ## # //\ # # ##
### # # // \ # ## ###
## # # // \ # # ## ##
# # # // \ # # #
### # # # // ## \ # # ###
# ### # // # # \ # # # ###
### # // # # | # # ###
# // # ## | #
Glucose Sensor # @ / # # | #
## | ## # | #
# / # # | #
#/ # # | #
Emg#@ # # | #
# # ## | #
## # | #
# # # | #
# # #\ #
# # # | #
# # # @ # Motion Sensor
## # ## ##
## #
Figure 2: Patient monitoring use case - Spoke Hub
Refer following diagram:
########
# @ EEG #
## |\-----@ # Hearing
# | \#
# | # |
# | ## |Motion Sensor
####### | ##|####
# | | ##
Positioning# @ | @ #
# /\ ECG| \ #
# / \----------@ \ #
# / | #
# / ## ## | #
# / # # # # @ # BP
#/ ## # # ## | ##
SPO2# @ ## # # ## | #
# \ # # # #| #
## ## \ # ## | # ##
## # \ # # | # ## ##
### # # # \ ## # | # ###
# ### # \ # # # | # # ###
### # | # # # | # ###
# | # ## # |
Glucose Sensor # @ # # # |
# / # # # /
#| ## # #/
#/ # # #|
Emg#@ # # #|
# \ # # #|
# \ # # #|
# \# ## #|
## \ # #|
# #\ # #|
# # \ # #|
# # \ # #|
# # \ ## #/
# # \ ## /
# # \ ## /#
## # \ | #
# # # \/ #
# # # @ # Motion Sensor
## #
Figure 3: Patient monitoring use case - Connected