WBAN system using GPPM algorithm for IEEE 802.15.TG6

WBAN system using GPPM algorithm for IEEE 802.15.TG6
ABSTRACT
Jae Ho Hwang ∗
INHA-WiTLAB, INHA University
253, younghyun-dong, Nam-gu
Incheon, Republic of Korea
hoho3676@naver.com
We propose a WBAN system which supports scalable datarate
modes and is based on the IR-UWB technique. Two
modulation schemes are proposed; an alternated PPM scheme
and a group PPM scheme. We introduce the alternated
PPM by reconfiguring an IEEE 802.15.4a system. And, we
propose an group PPM modulation scheme which represents
a new modulation method to IR-UWB radio architecture
and can meet the BAN. This algorithm increases entropy
and can increase data-rate. Lastly, we simulate two systems
in WBAN channel, and compare with technical requirement,
and also analyze both the systems by calculating a link budget.
Keywords
WBAN, UWB, PPM, GPPM, Link budget
1. INTRODUCTION
As the growing demand on communication services, various
wireless networking technologies are being developed.
Recent advances in wireless technology have led to the development
of wireless body area networks (WBAN), where
a set of communicating devices are located around the human
body. Especially, convergence between IT (information
technology) and BT (bio technology) attracts the attention
of many people to the health care services [1].
IEEE has launched the task group (TG) for WBAN in
IEEE 802.15 to satisfy the technical trend [2]. It develops
guideline for using wireless technologies for medical device
communications in various healthcare services, and also define
new communication standard with physical layer and
medium access control (MAC) protocol for both medical and
nonmedical applications within a range of 3 meters.
WBAN system can be categorized into medical BAN and
non-medical BAN by its applications. In the case of medi-
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Copyright 2010 ICST 978-963-9799-41-7 .
Jae Moung Kim
INHA-WiTLAB, INHA University
253, younghyun-dong, Nam-gu
Incheon, Republic of Korea
jaekim@inha.ac.kr
cal applications, these devices are connected to sensors that
monitor vital body parameters and movements. Nonmedical
BAN can be regarded as wearable consumer electronics,
sports, and entertainment devices for the on-body communications.
It can also be categorized three parts such as
in-body, on-body, and off-body by its positions [3].
The WBAN system needs transmission technique for ultra
low power devices and operation around the human body.
The ultra wideband (UWB) system has some advantages
such as low power radiation, and it exhibits immunity to
the multi-path channel environment. It is operating in an
unlicensed, international frequency band Therefore pulse position
modulation (PPM) is proposed for UWB frequency
band. The proposals are variations or modifications of IEEE
802.15.4a.
In this paper, we introduce the alternated PPM scheme
and investigate new modulation for the WBAN physical
layer. This paper is organized as follows. Section II explains
a technical requirement and trend in a standardization work.
The alternated PPM scheme is discussed and the new group
PPM (GPPM) method is proposed in section III. Eventually,
both of the modulation schemes are discussed by using
a simulation results and the link budget.
2. WBAN TECHNICAL REQUIREMENT
WBAN technical requirement document (TRD [4]) describes
the technical aspects that the TG6 standard must
fulfill. The requirements are summarized in table 1. The
WBAN system has short transmission range which is up to
3 meters. In this range, a packet error rate (PER) shall
be less than or equal to 10% for 256 octet payload with a
link success probability of 95% over all channel condition as
specified in the WBAN channel model.
WBAN applications have very different requirements. Medical
and vital signals tend to be periodic and low frequency;
interval can vary 1ms to 1000sec. Non-medical applications
such as interactive games, sports and real-time multimedia
application require high data rate transmission. Therefore
individual link bit rate should be between at least 10 Kbps
at the low end, and 10Mbps at the high end.
And available frequency bands are MICS (medical implant
communication service), MEDS (Medical data service),
WMTS (wireless medical telemetry service) for medical
application, and ISM (industrial, scientific, and medical),
UWB bands for unlicensed band. Medical WBAN applications
have substantial privacy and safety. During the transmission
of encrypted physiological data, patient identifiers
should be particularly protected from overhearing. further-

Table 1: WBAN technical requirement
requirement Proposed range
Operating space Up to 3m
Data rate Scalable (Up to 10Mbps)
Target bands MICS, MEDs, ISM, UWB
Device duty cycle Scalable (Up to 100%)
Peak power consumption Scalable (Up to 40mW)
Security High
Safety High
Topology Multiple Simultaneous links
more WBAN topology supports the multiple simultaneous
links.
3. WBAN PHY SYSTEM
Standard for WBAN developed by the IEEE802.15 task
group 6 which was formed in November 2007. There are
three categories of potential candidates. One of them is narrow
band system which used ISM band. The other is UWB
based technique. Last one is body line communication. One
of the potential candidates is using UWB based technique.
This overcomes the bandwidth limitations of narrow band
systems, and improves the power consumption. Another advantageous
is that UWB has immune to any interference on
other wireless medical devices.
The proposed IR-UWB systems are based on the modifications
of IEEE 802.15.4a standard. IMEC proposed enhanced
modulation scheme compared to that of the IEEE
802.15.4a. This technique converts the separate bursts into
concatenated continuous string so that it can increase the
data rate of the system [5]. A modified symbol structure
from the IEEE 802.15.4a is proposed by TI. It removes guard
interval between possible burst positions. Moreover, they
suggest a new time hopping sequence to avoid ISI caused by
removing the guard interval [6].
3.1 Alternative PPM scheme
Draft document of LR-WPAN UWB system are released
by IEEE 802.15.4a tasking group. This document is categorizing
UWB PHY system to three parts such as, impulse
radio (IR) system, chirp spread spectrum (CSS) system, and
chaotic signal system. Especially IR system has many strong
points as good performance in correlation result. Therefore
it is used widely in many applications [7].IR system is using
2PPM modulation which is sending data to locate pulse
in different two positions. The IR-UWB systems are using
burst pulse which is a serial of the pulse as code. It has
the advantage like strong to noise and useful to multi-user
system.
Figure 1 illustrates the UWB payload frame structure of
the 2PPM method. The PPM method consists of two regions.
For instance, if bit is zero then a burst pulse position
is front PPM position and bit is one a burst pulse is located
in the end. PPM region also divided four hopping region for
multi-user system. On burst region combine serial of UWB
pulse.
The UWB PPM method transmits the waveform during
the kth symbol interval, and may be expressed as follows:
Figure 1: PPM frame structure of the WBAN system
Table 2: Parameter of the alternated PPM scheme
10kbps 100Kbps 1Mbps 10Mbps
Viterbi 0.5 0.5 0.5 0.5
RS coding 0.87 0.87 0.87 0.87
Overall 0.435 0.435 0.435 0.435
nSymbol 32768 4096 256 32
nBurst 1024 128 8 1
nHop 8 8 8 8
Symbol rate (bps) 15.08k 120.6k 1.93M 15.42M
Bit rate (bps) 13.12k 104.9k 1.68M 13.43M
s (k) (t) =
Nburst n=1
Snp(t − g (k) TP P M − h (k) Tburst − nTc) (1)
the superscript (k), 1 ≤ k ≤ Nk, indicates incoming data
bits, where Nk is the number of the input bits. g (k) is the
mapping symbols obtained the kth data bit, Sn is the scrambling
sequence, p(.) is the transmitted pulse shape function,
TP P M is the duration of the binary pulse position modulation
time slot, and h (k) is the hopping sequence that provides
suppression of multi-user interference.
The alternative PPM algorithm for the WBAN system is
modified version of the low data rate UWB system. To get
the multi data rate from 10kbps to 10Mbps, symbol lengths
are reconfigured as shown in table 2. Concatenated codes
are used for error correction which consist of the convolution
code and the RS code which codes have 0.5 and 0.87 coding
rate. These parameters are same to the IEEE802.15.4a
standard respectively [7].
Frame structures are reconfigured to support multi data
rates. Chip duration is 2.024nsec which has one UWB pulse,
and number of hopping is 8 chips. To get the 10Mbps data
rate, symbol length set to 32 chips and the number of burst
length set to one chips. Therefore, symbol rate will have
15.42 Mbps, bit rates is 13.43 Mbps after passing the channel
coding block. Others also similar to 10Mbps mode, the
1Mbps mode is same to the IEEE 802.15.4a mandatory system.
And 100kbps mode consist of 4096 symbol chips and
128 burst chips to get the 100Kbps data rate after channel
coding. 10Kbps mode need 1024chips burst symbol in the
32768 chips frame.
3.2 Group PPM scheme
In this section, the group PPM method is proposed for increasing
entropy by using grouping with a continuous symbol
set. The number of cases increase when symbols are

Figure 2: conventional PPM symbols and proposed
GPPM extra symbols
grouped. Two symbols from the PPM system will express
four numbers of cases as symbol codes: (s11, s12, s21, and
s22) equates to (’0101’, ’0110’, ’1001’, and ’1010’), which
represent the pulse position. The grouping PPM method,
however, has extra symbol codes, such as (’1100’, ’0011’).
In this case, group 2PPM increases entropy as follows. The
conventional PPM symbol and extra symbols which is generated
by grouping is shown in the figure 2.
In equation (2), the entropy of the GPPM is 2.5849; this is
larger than the entropy of a conventional two-symbol system.
H(S2GP P M ) =
6
i=1
P2GP P M,iI(P2GP P M,i)
= 6 × 1
log 2(6) = 2.5849
6
Generally, number of symbol cases of m-GPPM have (Nm)
value, as shown in equation (3).
Nm =
2m × (2m − 1) × . . . × (m − 1)
m × . . . × 2 × 1
And, entropies of m-GPPM are also explained as shown
in equation (4).
H(Sm GP P M ) =
m
i=1
= Nm × 1
Pm GP P M,iI(Pm GP P M,i)
Nm
log 2(Nm)
In Table 3, the number of cases and the amount of entropy
is compared for each group when using the GPPM and the
conventional PPM. The m-GPPM has an extra symbol set
and increases entropy.
The calculated entropy shows that the GPPM method
maximizes the information and entropy without an increase
in energy consumption. Two grouping symbols have 0.5849
increases, but this does not increase data-rate in a binary
system. However, three and more grouping symbol has integer
number of entropy augmentation; such arrangements
will obtain data-rate enhancements.
GPPM algorithm has advantage that the frame structure
modification is not required. Therefore frame structure is
(2)
(3)
(4)
same to PPM structure, but GPPM algorithm increase data
rate for example 3GPPM mode has 33% data rate increasement.
The frame length extension cause guard integral extension.
It has immunity of multi path fading channel distortion.
Therefore this system does not requires channel
coding.
This new modulation method can be expressed by a mathematical
equation. The frame structure, length, scramble
and hopping codes are the same in the proposed system as
in the conventional method. The equation expressing the
new modulation method is shown below in equation (5).
s (k) (t) =
3
m=1
Nburst n=1
Snp(t − g (k)
m TP P M − h (k) Tburst − nTc)
Where, theg (k)
m represents the mapping data generated to
change the four-input binary data.
In this paper, we use 3GPPM algorithm to increase data
rate. Table 4 shows the specific parameter for each data
rate mode. The frame structure is same to the alternate
PPM mode as shown in the figure 1. The alternated PPM
scheme has 32 chips in whole frame length to get the 10Mbps
data rate, but GPPM mode extends 64 chips. This case
symbol rate does not satisfy 10Mbps, but data rate increase
to 10.27Mbps by using the GPPM algorithm. Other modes
also increase frame length compare with the alternated PPM
mode.
4. SIMULATION AND ANALYSIS
In this paper, the alternated PPM scheme and GPPM
scheme are described in each data rate mode. The alternated
PPM scheme use conventional PPM with channel coding,
but modified parameter to fit the technical requirement.
And the GPPM scheme is proposed in each data rate mode.
This is using GPPM algorithm to increase frame length.
In this section, the performance of alternated PPM scheme
is verified in each data rate mode with AWGN channel and
WBAN channel. The proposed GPPM scheme also simulates
in the same situation, and compares with alternated
PPM scheme. Finally, two schemes will be compared in the
same situation by using the link budget.
Each result is simulated by using system parameter in table
2 and 4. And WBAN channel model and AWGN channel
are used. Especially body surface to external channel model
is used. This channel model consists of four situations such
as front, L-side, R-side, and backside of body [8], and received
algorithm is using simple energy detector.
4.1 alternative PPM scheme
Table 3: Entropy of Method Each Group
Number PPM Group PPM
of Group # of Case Entropy # of Case Entropy
1 2 1.0000 2 1.0000
2 4 2.0000 6 2.5849
3 8 3.0000 20 4.3219
4 16 4.0000 70 6.1292
5 32 5.0000 252 7.9772
(5)

Table 4: Parameter of the GPPM scheme
10Mbps 100Kbps 1Mbps 10Mbps
GPPM rate 1.33 1.33 1.33 1.33
nSymbol 655536 4096 512 64
nBurst 2048 128 16 2
nHop 8 8 8 8
Symbol rate (bps) 7.53K 120.6K 0.96M 7.72M
Bit rate (bps) 10.03K 160.4K 1.28M 10.27M
Figure 3: PER performance of the alternated PPM
in AWGN channel
First, the alternative PPM scheme is simulated to get
the PER curve in the AWGN channel and WBAN channels.
Various data rate modes are simulated such as 10K,
100K, 1M, 10Mbps mode.
Figure 3 is shown the PER performance of alternated
PPM scheme. The required PER performance is below 10%
when the packets consist of 256 octets which are described
in the technical document. 10Kbps mode satisfies 10% PER
when SNR is under -20dB. It is very good performance, because
this mode has used 2048 burst chips which will use
average effect. 100Kbps mode and 1Mbps also has good
performance. The 10Mbps mode satisfy 10% PER performance
at 9 dB SNR
Especially 10Mbps mode is critical to satisfy technical requirement
due to the short guard interval. If rms delay of
the multi-path channel is longer than guard interval, performance
will reduce. Figure 4 shows the PER performance
of 10Mbps mode with WBAN channel. This channel model
consist of front (0 ◦ ), sides (90 ◦ , 270 ◦ ), and back (180 ◦ ) position
[9]. The figure shows that it has 10% PER performance
when SNR is 12dB.
4.2 GPPM scheme
In this chapter, the GPPM scheme is simulated in the
channel. Various data rate modes are simulated such as
10k, 100k, 1M, 10Mbps mode. Each mode uses the 3GPPM
algorithm and channel coding is not used.
Figure 4: PER performance of the group PPM in
WBAN channel
Figure 5 shows the PER performance of GPPM scheme
in the AWGN channel. Required PER performance is below
10% when the packets consist of 256 octets. The 10kbps
mode of the GPPM scheme satisfies 10% PER when SNR
is under -20dB. It also has good performance, because this
mode has used 2048 burst chips which will use average effect.
100Kbps mode and 1Mbps also has good performance.
But PER performance of the 100Kbps mode is lower than
alternative PPM scheme, because it frame structure are similar
to alternative PPM one but do not has error correcting
block. The 10Mbps mode also satisfies 10% PER performance
when the SNR is 9 dB.
Figure 6 shows the PER performance of 10Mbps mode
with WBAN channel when GPPM scheme is used. This
also simulated in each channel model such as front, sides,
and back position. This performance figure shows that it
has 10% PER performance when SNR is 10dB. The performance
of the proposed scheme is better than alternative
PPM scheme, as the frame length extension technique is
more effective than channel coding.
4.3 Link budget
Previous chapter show the simulation performance of each
scheme. Especially 10Mbps mode performance is very important
and sensitive. Therefore we analyze two schemes
by calculating link budget. This is calculated in table 5 the
peak bit rate of alternated PPM scheme is 13.4Mbps and
GPPM scheme is 10.27Mbps, which show that both schemes
are satisfied the WBAN technical requirement. Signal power
set to -14.3dBm and center frequency is used 4.4928 GHz.
And communication range is 3meter, and a path loss is -
55.0dB. Therefore received power is -69.3dB and noise power
is -92.1dBm. Finally the alternated PPM scheme has 6.8dB
link margin, sensitivity is -76.1dB. The GPPM scheme has
7.8dB link margin, sensitivity is -77.1dB. As like this, two
systems are satisfied for the WBAN PHY scheme.
5. CONCLUTION

Figure 5: PER performance of the GPPM in AWGN
channel
Table 5: Link Budget
Parameter Alternated PPM GPPM
Peak bit late 13.4(Mbps) 10.2(Mbps)
Distance 3m 3m
Average Tx Power -14.3(dBm) -14.3(dBm)
Center Freq. 4.4928(GHz) 4.4928(GHz)
Path loss -55.0(dB) -55.0(dB)
Rx power -69.3(dB) -69.3(dB)
Rx Noise Floor -87.0(dB) -87.0(dB)
Rx Noise Figure 10(dB) 10(dB)
Noise Reduction -15.1(dB) -15.1(dB)
Average Noise Power -92.1(dBm) -92.1(dBm)
Minimum Eb/N0 11(dB) 10(dB)
Implementation loss 5(dB) 5(dB)
Link Margin 6.8(dB) 7.8(dB)
Rx sensitivity -76.1(dB) -77.1(dB)
In this paper, we deal with about WBAN PHY structure
to satisfy technical requirement. The UWB based technique
is one of the potential candidate techniques. It has
advantages such as improves the power consumption, Interference
immunity, and ease of frame configuration. We
describe the two PHY scheme, one of them is the alternated
PPM scheme, which are based on the modifications of IEEE
802.15.4a standard. Another is GPPM scheme, based on
GPPM algorithm to increase data rate. The GPPM algorithm
uses the symbol grouping with the conventional PPM
to increase the entropy of the system. We simulate two
schemes in the WBAN environment. We analyze the potential
of two scheme for the WBAN system by calculate
link budget. It is shown the UWB based system has advantage
and satisfies the WBAN requirement. Especially
the GPPM algorithm is more fit to WBAN system, because
GPPM scheme is simple which is not used channel coding,
addition to better performances.
Figure 6: PER performance of the GPPM in WBAN
channel
Acknowledgment
This research was supported by Basic Science Research Program
through the National Research Foundation of Korea
(NRF) funded by the Ministry of Education, Science and
Technology (No. 20090066336).
This research was supported by the MKE(The Ministry of
Knowledge Economy), Korea, under the ITRC(Information
Technology Research Center) support program supervised
by the NIPA(National IT Industry Promotion Agency) (NIPA-
2010-C1090-1011-0007)
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