this is project report on bluestar. make use of better.

1. BLUESTAR
CHAPTER-1
INTRODUCTION
Bluetooth is a wireless communication technology that provides short-range, semi-
autonomous radio network connections, and offers the ability to establish ad hoc networks,
called piconets. It has also been chosen to serve as the baseline of the IEEE 802.15.1 standard for
wireless personal area networks (WPANs). WPAN can be integrated with large wide area
networks (WANs) to provide Internet connectivity in addition to access among these devices. It
is much likely that Bluetooth devices and wireless local area networks (WLANs) stations
operating in the 2.4 GHz frequency band should be able to coexist as well as cooperate with each
other, and access each other’s resources. These cooperative requirements have encouraged an
intuitive architecture, called Bluestar, whereby few selected Bluetooth devices, called Bluetooth
wireless gateways (BWG), are also members of a WLAN, empowering low-cost, short-range
devices to access the global Internet infrastructure through the use of WLAN basedhigh-powered
transmitters [1]. Bluetooth Wireless Gateways (BWGs), are also IEEE 802.11 enabled so that
these BWGs could serve as egress/ingress points to/from the IEEE 802.11 wireless network.
An important challenge in defining the Bluestar architecture is that both Bluetooth and
WLANs employ the same 2.4 GHz ISM band and can possibly impact the performance. The
interference generated by WLAN devices over the Bluetooth channel called as persistent
interference, while the presence of multiple piconets in the vicinity creates interference referred
to as intermittent interference. To combat both of these interference sources and provide
effective coexistence, authors proposed a unique hybridapproach of adaptive frequency hopping
(AFH) and a new mechanism called Bluetooth carrier sense (BCS) in Blue-Star. AFH seeks to
mitigate persistent interference by scanning the channels during a monitoring period. BCS takes
care of the intermittent interference by sensing channel before transmission.
Bluestar takes advantage of the widely available WLAN installed base as it is advantageous
to use pre-existing WLAN infrastructure. This can easily support long-range, large-scale
mobility as well as provide uninterrupted access to Bluetooth devices.
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2. BLUESTAR
CHAPTER-2
BLUETOOTH
Ad hoc networks such as Bluetooth are networks designed to dynamically connect remote
devices such as cell phones, laptops, and PDAs. These networks are termed “ad hoc” because of
their shifting network topologies. Whereas WLANs use a fixed network infrastructure, ad hoc
networks maintain random network configurations, relying on a master-slave system connected
by wireless links to enable devices to communicate. In a Bluetooth network, the master of the
piconet controls the changing network topologiesof these networks. It also controls the flow of
data between devices that are capable of supporting direct links to each other.
Bluetooth was designed as a low-cost, low-power wireless networking technology to be used
in a person’s operating space,i.e. the space that typically extends up to 10m. Bluetooth is a short-
range (up to 10 m) wireless technology aimed at replacing cables that connect phones, laptops,
and other portable devices [3]. Bluetooth operates in the ISM frequency band 2.4 GHz. The
Bluetooth radio transmission uses a slotted protocol with a FHSS (Frequency Hopping Spread
Spectrum) technique. A total of 79 RF channels of 1 MHz width are defined, where the raw data
rate is 1 Mbit/s. Channel is divided into 625 µs slots and, with a 1 Mbit/s symbol rate, a slot can
carry up to 625 bits. Transmission occurs in packets that occupy 1, 3 and 5 slots. Each packet is
transmitted on a different hop frequency with a maximum frequency hopping rate of 1600
hops/s.
Fig-1 Packet transmission in Bluetooth
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3. BLUESTAR
Communication of Bluetooth devices follows a strict master-slave scheme, i.e. there is no
way for slave devices to communicate directly with each other. Master periodically polls the
Slave devices and only after receiving such a poll is a Slave allowed to transmit. The Master for
a particular set of connections is defined as the device that initiated the connections. A Master
device can directly control up to seven active Slave devices. The Bluetooth network supports
both point-to-point and point-to-multi-point connections. In order to fulfill this function, two
terms are defined:
2.1 Piconet
The Bluetooth devices which have been setup using the same frequency hopping channel
and clock form a Piconet. In every Piconet, one Bluetooth device is in charge of setting the
communications, deciding the queue of frequency hopping and synchronizing the network. It is
so-called Master. Other devices are joined to this piconet as slave.
2.2 Scatternet
Agroup of Piconet in which connections consists between different Piconet is called a
Scatternet. Between two Piconet in a Scatternet, at least one Bluetooth device is acting as a
bridge to connect two Piconet. Each piconet is established by a different frequency hopping
channel. All users participating on the same piconet are synchronized to this channel.
The Bluetooth specification defines two distinct types of links for the support of voice
and data applications, namely, SCO (synchronous connection-oriented) andACL (asynchronous
connectionless). The first link type supports point to point voice switched circuits while the latter
supports symmetric as well as asymmetric data transmission. The frequency hopping scheme is
combined with fast ARQ (Automatic Repeat Request), CRC (Cyclic Redundancy Check) and
FEC (Forward Error Correction) to achieve appropriate reliability on the wireless link.
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4. BLUESTAR
2.3 Bluetooth Stack
Bluetooth is a lower-layer specification by the view of OSI. Figure below shows the
main protocols of Bluetooth. The key parts of it are radio (RF) layer, baseband and link
layer(link manager and L2CAP).
Fig-2: Bluetooth protocol
Radio or RF part of Bluetooth is the lowest layer that defines the frequency bands and
channel arrangement, transmitter and receiver characteristics.
Baseband define packet format, physical and logical channels, channel control, hop
selection etc. It establishes the Bluetooth physical link between devices forming a
piconet.
Link Manager Protocol (LMP) is used for link set-up and control. Other functions of the
link manager include security, negotiation of Baseband packet sizes, power mode and
duty cycle control of the Bluetooth device, and the connection states of a Bluetooth
device in a piconet..
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5. BLUESTAR
The interfaces between the hardware and software are such common ones as
USB and UART which are include in Host Controller Interface (HCI) to make them
universal to the different vendor.
L2CAP supports higher-level protocol multiplexing, packet segmentation and
reassembly, and the conveying of quality of service information. It provides the upper
layer protocols with connectionless and connection-oriented services.
Bluetooth also includes other important protocols, such as service discovery protocol
(SDI), audio and some Bluetooth-specific adaptation protocol (RFCOMM).
RFCOMM protocol, which allows for the emulation of serial ports over the L2CAP. It is
a transport protocol that provides serial data transfer. In other words, it enables legacy
software applications to operate on a Bluetooth device.
The Service Discovery Protocol (SDP) provides the means for Bluetooth applications to
discover the services and the characteristics of the available services that are unique to
Bluetooth.SDPprovides service discovery specific to Bluetooth. That is, one device can
determine the services available in another connected device by implementing the SDP.
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6. BLUESTAR
CHAPTER-3
Wireless LAN
WLANs allow greater flexibility and portability than do traditional wired local area networks
(LAN). Unlike a traditional LAN, which requires a wire to connect a user’s computer to the
network, a WLAN connects computers and other components to the network using an access
point device[5]. An access point communicates with devices equipped with wireless network
adaptors; it connects to a wired Ethernet LAN via an RJ-45 port. Access point devices typically
have coverage areas of up 100 meters. This coverage area is called a cell or range. Users move
freely within the cell with their laptop or other network device. Access point cells can be linked
together.
WLANs are based on the IEEE 802.11 standard, which the IEEE first developed in 1997.
The IEEE designed 802.11 to support medium-range, higher data rate applications, such as
Ethernet networks, and to address mobile and portable stations. 802.11 is the original WLAN
standard, designed for 1 Mbps to 2 Mbps wireless transmissions. 802.11b standard was
completed in 1999, which operates in the 2.4 - 2.48 GHz band and supports 11 Mbps. The
802.11b standard is currently the dominant standard for WLANs, providing sufficient speeds for
most of today’s applications.
Fig-3 wireless LAN
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7. BLUESTAR
CHAPTER-4
The proposed Bluestar architecture
BlueStars produces a mesh-like connected scatternet with multiple routes between pairs
of nodes. It is a distributed solution. That is, all the nodes participate in the formation of the
scatternet. But they do so with minimal, local topology knowledge (nodes only knowabout their
one-hop neighbors). BlueStars, a new scatternet formation protocol for multi-hop Bluetooth
networks, that overcomes the drawbacks of previous solutions in that it is fully distributed, does
not require each node to be in the transmission range of each othernode and generates a
scatternet whose topology is a mesh[4].
The protocol proceeds in three phases:
1. The first phase, topology discovery, concerns the discovery of neighboring devices. This
phase allows each device to become aware of its one hop neighbors’ ID and weight.By
the end of this phase, neighboring devices acquire a “symmetric” knowledge of each
other.
Fig-4 First Phase Topology
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8. BLUESTAR
2. The second phase takes care of BlueStar (piconet) formation. Given that each piconet is
formed by one master and a limited number of slaves that form a star-like topology, we
call this phase of the protocol BlueStars formation phase. Based on the information
gathered in the previous phase, namely, the ID, the weight, and synchronization
information of the discovered neighbors, each device performs the protocol locally. A
device decides whether it is going to be a master or a slave depending on the decision
made by the neighbors with bigger weight. By the end of this phase, the whole network is
covered by disjoint piconets.
Fig-5 Second phase Topology
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9. BLUESTAR
3. The final phase
The final phase concerns the selection of gateway devices to connect multiple BlueStars.
The purpose of the third phase of our protocol is to interconnect neighboring BlueStars by
selecting inter-piconet gateway devices so that the resulting scatternet is connected whenever
physically possible. The main task accomplished by this phase of the protocol is gateway
selection and interconnection.
Fig-6 Third Phase Topology
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10. BLUESTAR
This noval architecture is expected to be capable of accessing networked information,
especially through a WAN such as the Internet. This allows dynamic content to be delivered to
the piconets and to the devices that may not otherwise have such WAN access, but can
communicate with other Bluetooth devices that do have access, either within the piconet or
scatternet. Bluetooth access to the WAN and take advantage of the existing IEEE 802.11
WLANs by using bluetooth selected devices – which possess botha WLAN interface and a
Bluetooth interface – as Bluetooth wireless gateways (BWGs). The interaction between the
Bluetooth network and the outside world is managed by the BWGs[1]. Figure below illustrates
the BlueStar architecture with a scatternet, composed of total of four piconet, where each piconet
has several slaves (indicated by the letter Si,j) and one master (indicated by the letter Mi ). In this
figure, two BWGs provide the scatternet Bluetooth devices access to the local WLAN which, in
turn, provides communication to the local LAN, MAN, or WAN, and possibly the Internet.
Fig-7 Bluestar proposed architecture
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11. BLUESTAR
The interaction between the Bluetooth network and the outside world is managed by the
BWGs. The possible protocol stacks to carry IP packets over Bluetooth could be employed
within BWGs. the Bluetooth SIG has published a native way for carrying IP traffic over
Bluetooth by a protocol called Bluetooth network encapsulation protocol(BNEP) wherein IP
packets are encapsulated in Ethernet packets which are then carried over Bluetooth links.
Fig-8 Protocol stack for each entity
In order for Bluetooth devices to be directly addressed, authors assumed that every
Bluetooth device possesses an IP address and any of the well-known routing algorithms is
available
A crucial challenge in the design of BlueStar is to enable an efficient and concurrent
operation of both Bluetooth and WLANs as they both employ the same 2.4 GHz ISM band. To
combat the interference sources, BlueStar employs a unique hybrid approach of an adaptive
frequency hopping (AFH) and the Bluetooth carrier sense (BCS).
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12. BLUESTAR
4.1.Bluetooth carrier sense (BCS)
BlueStar employs carrier sense so that intermittent-like interference can be avoided.
Carrier sensing is fundamental to any efficient interference mitigation with other technologies
using the same ISM frequency band, and among Bluetooth piconets Themselves[1]. Author has
incorporated BCS into Bluetooth without any modifications to the current slot structure. Carrier
sensing is shown in figure :
Fig-9 Carrier sensing mechanism in Bluetooth
In figure the dashed block denotes the sense window of size WBCS. Before starting
packet transmission, the next channel is checked (i.e., sense) in the turn around time of the
current slot. If the next channel is busy or becomes busy during the sense window, the sender
simply withholds any attempt for packet transmission, skips the channel, and waits for the next
chance. Otherwise, packet transmission is carried out. A direct consequence of this approach is
that, eventually, an ARQ (automatic retransmission request) packet will be sent when the slot is
clear and the communication is carried out.
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13. BLUESTAR
The nature of intermittent interference :
As packet transmission in different piconets are asynchronous and are transmitted with
period Tp, which depends upon the Bluetooth packet type p. For instance, if p is equal to DH1 or
DM1 we have that Tp= 2 · slotsize, where slotsizeis the size of a Bluetooth slot, and is equal to
625 µsec. Figure 4 illustrates the timing of two Bluetooth packets p and z generated at piconetsi
and j with sizes Sp,iand Sz,j, respectively.
Fig-10 Timing of two Bluetooth pockets on different piconets
The probability of packet collision between piconetsI and j is :
pc(i, j ) = (Sp,i+ Sz,j ) /((max _slotsperpacket(p),slotsperpacket(z)) + 1)* slotsize)*1/C
whereC is the number of available frequency channels
slotsperpacket(X) gives the number of slots occupied by a Bluetooth packet X
The packet collision probability with a packet originated at the ithpiconet is given by (N
piconets) :
pc(i) = 1 − (1 - pc(i, j ))N−1
.
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14. BLUESTAR
Fig-11 Packet collision and withdrawal probabilities for different slot length packets
As we can see from figure 5, even though both packet probabilities increase with the
number of piconets, the packet withdrawal probability increases at a slower rate, indicating that a
large fraction of packet collisions are being avoided with the adoption of BCS. Moreover, the
rate of increase is also distinct for different slot length packets. Bluetooth with BCS not only
significantly increases the overall throughput but alsonables a larger number of nearby piconets
to operate efficiently.
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15. BLUESTAR
4.2. Bluetooth adaptive frequency hopping (AFH)
Given that a IEEE 802.11 DATA frame has a maximum size of up to 2346 octets and a
Bluetooth slot occupies 625 bits , in the worst case, so a IEEE 802.11 DATA frame can overlap
with up to 30 Bluetooth slots[1]. Figure 7 shows two potential cases of packet collisions.
Fig-12 Potential packet collisions between IEEE 802.11 and Bluetooth
Although the IEEE 802.11WLAN senses the channel before transmission, it cannot
sense the Bluetooth activities, since the Bluetooth signal is narrowband and low power as
compared to WLANs. Therefore, when the Bluetooth packet (from piconeti) is ahead of the
WLAN, packet collision (with the next IEEE 802.11 packet) takes place even after employing
BCS. On the other hand, when the WLAN packet is ahead of the Bluetooth packet BCS
successfully senses activity in the medium and withdraws packet transmission.
Bluetooth devices scan every T SCAN seconds for each of the 79 channels used by
Bluetooth and collect PER statistics. If the PER is above a threshold PERTHRES, it is labeled
as “bad”; otherwise it is labeled as “good”. All devices within a piconet carry out this procedure
and when the piconet master request this, the slaves send their measured “good” and “bad”
channel marks. The master, in turn, conducts a referendum process based on information
collected by itself and provided by the slaves. The final mapping sequence is then determined
and sent back to each slave device, which follow this new sequence thereafter. Authors have
implemented this scheme by a bitmap comprising of 79 bits where a one indicates that a
frequency can be used while a zero indicates otherwise. The overall effect on Bluetooth is that
the total number of available channels C decreases as some channels may be labeled as “bad”.
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16. BLUESTAR
4.3 Capacity allocation scheme
In the BlueStar architecture, theBWGs have to act as forwarding units between the
wireless systems besides serving as source or destination for their own applications. Thus, a
BWG must spend a proportional amount of time in receiving data as in forwarding it[1].
Obviously, because of mismatch in packet sizes and the eventual segmentation and reassembly
overheads, the time spent in one network may not be exactly the time spent in the other. Since a
BWG can be present only in one piconet at a time, the total capacity a BWG can provide to the
users it serves is bounded by half the piconet capacity. This prevents the fair distribution of the
capacity when a BWG serves more than half the total number of users in the scatternet.
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17. BLUESTAR
CHAPTER-5
Simulation of BlueStar
Authors have implemented all functionalities of BlueStar in the network simulator (ns-2)
andBlueHoc. In addition, authors consider that the interfering range of Bluetooth devices is
about two times larger than the transmission range and an IEEE 802.11b DSSS running at 11
Mbps for all simulations[1]. Authors have developed a hybrid Bluetooth-802.11 model that has
been incorporated into the BWGs.
5.1Bluetooth-only simulation environment
Initial experiment employs an environment comprised of only Bluetooth devices without
any external sources of interference. Therefore, since we are mainly concerned with intermittent
interference and BCS, AFH is not employed. Figure 8 illustrates the topology used for this
evaluation. Within a total area of 500 m × 500 m, we have considered a network composed
initially of 10 piconets. For each of the twenty simulation runs, we increase the number of
piconets by 10 up to a total of 200 piconets, where each piconet comprises of four devices.
Fig-13 Bluetooth only network topology model
Bluetooth with BCS greatly reduces the number of collisions and defers packet transmission
until a safe channel is found and BCS can drastically increase throughput.
.
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18. BLUESTAR
5.2 Combined Bluetooth and WLAN simulation environment
In this section authors carried out experiments with both intermittent and persistent
interferences. For that, we utilize the implementations of both BCS and AFH[1].
TCP/IP traffic simulation
Similar to earlier simulations, we have considered a network initially comprising of 10
piconets, and increase the number of piconets in steps of 10 till 200 piconets. As for the WLAN
axis, it is composed of an AP, located at (0, 200) m, which has a radio range of 250 m.
Fig-14 WLAN and Bluetooth network simulation model
The traffic between the WLAN AP and Bluetooth network also consists of FTP traffic.
The WLAN packet is of total size of approximately 1.5 KByte. Authors had set the offered load
in each piconet to 30% of its total capacity, and assume Bluetooth stations to be stationary as
currently assumed by BlueHoc.
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19. BLUESTAR
Four possible scenarios as follows:
Scenario A:
The flow of data packets is from the WLAN AP to the BWG, reflecting an application
where Bluetooth devices downloading contents from the WAN.
Scenario B:
This scenario is the opposite of the previous one with the Bluetooth devices uploading
information to the WAN, i.e., the flow of data packets is from the BWG to the WLAN AP.
Scenario C:
A BWG might find itself in a situation where it simultaneously receives data packets
from both the WLAN AP and the Bluetooth devices in order to synchronize information in the
BWG.
Scenario D:
This scenario models the opposite situation as described in scenario C. In other words, it
is the case where the BWG simultaneously transmits data packets to both the Bluetooth devices
and the WLAN AP.
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20. BLUESTAR
Results obtained for different scenarios after Simulation are:
Scenarios B and D:
scenarios B and D experience a sizeable degradation in throughput as compared to
scenarios A and C, with scenario B having the largest impact. This is particularly true in these
scenarios because when the BWG is transmitting data packets towards the AP, there is a high
persistent interference in the Bluetooth network causing a high PER. On the other hand, in
scenarios A and C the BWG is sending acknowledgments (ACKs) to the AP, therefore reducing
the probability of packets being corrupted. The reason why scenario B suffers a higher
performance drop (and higher PER) than scenario D is because the WLAN transmissions corrupt
the Bluetooth data packets in scenario B, while in scenario D only Bluetooth ACK packets are
susceptible to be corrupted by WLAN transmissions.
Since these scenarios are more impacted by persistent interference, AFH is effective for a larger
number of piconets until it reaches a point where the intermittent interference levels becomes
significant. At these points, BCS performs better by effectively mitigating intermittent
interference sources. Despite the high interference levels, BlueStar, employing both AFH and
BCS, accomplishes enhanced performance by achieving the highest throughput and lowest PER.
Scenarios A and C :
AFH is now effective only for a smaller number of piconets as the larger impact comes
from intermittent interference. In scenarios A and C (especially in scenario A) the regular
Bluetooth implementation shows performance sometimes comparable to that of the AFH
scheme, which is primarily due to the TCP congestion control mechanisms employed in the
WLAN interface. When collisions in the WLAN traffic occur, the frame has to be completely
retransmitted as IEEE 802.11 WLANs do not employ any kind of FEC (forward error
correction). In scenario A the WLAN transmissions have been corrupting the Bluetooth ACK
packets, while in scenario C Bluetooth data packets are more impacted. Therefore, scenario A
performs slightly better due to the shorter and less frequent duration of the ACK packets.
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21. BLUESTAR
Scenarios C and D:
A higher drop in throughput for scenario D, especially for the ordinary Bluetooth
implementation. As expected, AFH outperforms BCS when most of the interference is of
persistent type, however degrades nearly at the same rate as the ordinary Bluetooth
implementation when the number of piconets become larger than 50 and 65 for scenarios C and
D, respectively. Likewise, BlueStar approximately doublesthe throughput achieved in Bluetooth
by combining AFH and BCS.
Moreover, it is also important to highlight the performance of AFH as it outperforms
BCS under a small number of piconets, since most of the interference is of persistent type.
However, as the number of piconets increase, and hence the intermittent interference level, the
performance of AFH degrades and BCS becomes more efficient both in terms of PER and
throughput. More specifically, in scenarios B and D AFH is more efficient than BCS up to 90
and 72 piconets respectively, whereas in scenarios A and C AFH performs better when the
number of piconets is approximately less than 55.
In all scenarios, BlueStar achieves the best throughput and the lowest PER by taking
advantage of both AFH and BCS.
5.3 Placement and number of BWGs in bluestar
This section deals with number of BWGs are needed to provide adequate and uninterrupted
coverage to all devices in a Bluetooth scatternet, as well as where to place these BWGs. Authors
refer to these as the placement and the number problems. The topology of interconnection has
influence on the number of resulting BWGs. Authors has proposed a model in which a BWG
serve as bridge node between exactly two neighboring piconets and piconets have a circular
shape and are centered on the master[1]. BWG between two piconet
While in figure A the addition of a piconet resulted in the addition of only one more
BWG, the same piconet might also result in the addition of two more BWGs as shown in figure
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22. BLUESTAR
However, since major interest is in an upper bound (worst-case) on the number of
BWGs, this task is simplified by considering only the topology which results in the highest
interconnection, as exemplified in the sketch of figure C. In Bluetooth, it is possible to have all
eight devices of a piconet working as bridge nodes.
Fig D
Fig.A Fig. B
Fig. C
Fig-15 Placement and number of BWGs in Bluestar
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23. BLUESTAR
For mathematical simplicity, we impose a restriction that only the master device is not
allowed to work as a BWG. Thus, among seven BWGs of a piconet, each BWG is shared by two
piconets. It is clear that we can have at most [7n/2] BWGs in a scatternet composed of n
piconets. In fact, the total number of BWGs required will be fewer than these as there is no need
to have a BWG on non-bridge devices as shown in the outer parts of figures .
Proposition 1.
For a scatternet comprised of n (n >0) piconets, where piconets have a circular (or near-
circular) shape (figure B), the number of BWGs needed is at most [7n/2] − 2[4√n − 4] .
Proposition 2.
For a scatternet comprised of n (n >0) piconets, the maximum number of BWGs needed
is [7n/2] − 2[4√n − 4] .
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24. BLUESTAR
CHAPTER-6
Conclusion
This paper introduces a novel architecture called BlueStar, which employs a combinationof
adaptive frequency hopping and Bluetooth carrier sensing to efficiently provide advanced wide
area services to Bluetooth devices. BlueStar can take advantage of the existing installed base of
IEEE 802.11 wireless networks by assigning selected Bluetooth devices, called Bluetooth
wireless gateways (BWG), with IEEE 802.11 capabilities. These BWG are responsible for
providing uninterrupted access to the WAN, such as the Internet, to the entire Bluetooth network
(piconet or scatternet). BlueStar is observed to greatly outperform existing Bluetooth under
different traffic condition. The incorporation of BlueStar into Bluetooth is simple, does not incur
much overhead, and hence is an excellent enabler for co-existence and cooperation of Bluetooth
and IEEE 802.11.
Future work in BlueStar includes defining a more elaborate capacity allocation algorithm. In
addition, we plan to investigate the correlation amongst the various simulation parameters in
order to assess their impact on BCS and AFH. Mobility of both IEEE 802.11 and Bluetooth
devices and its impact on both systems are also part of our future research.
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25. BLUESTAR
CHAPTER-7
References
[1] Bluestar: enabling efficient integration between Bluetooth WPANs
and IEEE 802.11 WLANs
Mobile Networks and Applications archive
Volume 9 , Issue 4 (August 2004) ,Pages: 409 – 422
Carlos De M. Cordeiro, SachinAbhyankar, Rishi Toshiwal,
Dharma P. Agrawal
[2] Ascatternet operation protocol for Bluetooth ad hoc networks
Wireless Personal Multimedia Communications, 2002
27-30 Oct. 2002,pages: 223 – 227, Volume: 1
Tadashi Sato, KenichiMase
[3] Bluetooth - The Fastest Developing Wireless Technology
May 2000 , pages: 1657 – 1664
ZhangPei, Li Weidong, Wang Jing, Wang Yotizhen
[4] Bluetooth scatternet models
December 2004/ January 2005, pages : 36 – 39
Patricia McDermott-Wells
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