cs 515 © İbrahim körpeoğlu1 bluesky: a new indoor wireless access network and mobility solution...

CS 515 © İbrahim Körpeoğlu 1

BlueSky: A new indoor wireless access network and mobility solution

İbrahim KörpeoğluCS 515 – Mobile and Wireless NetworkingBilkent University Computer Engineering DepartmentBilkent/Ankara


Putting the pieces together

BlueSky is an experimental protoype wireless access network designed at IBM T.J. Watson Research Center, Hawthorne, New York, in 1998.

It has been started before Bluetooth Special Interested group (SIG) has been formed.

In this course, we are now at a level to understand the design of wireless systems from bottom to nearly top.


Why BlueSky? Aims providing wireless indoor access for palmtop

computer (PDAa) such as palm pilots. Low power and low cost are primary objectives. No service fee.

802.11 is expensive, power hungry Cellular modems have expensive service charge.

Aims providing indoor seamless mobility support for Bluesky enabled devices and computers.

Least modification to end-devices with different operating systems.

PPP constrained.


Why networking for PDAs?

There are different kinds of palmtop computers. Also called personal digital assistants. Examples

Palm Pilots: running PalmOS Pocket PC: running Windows CE

We concentrated on a solution for Palm Pilots.


PDA

Ethernet Card

Palm Pilot Networking at that time

Serial Port(UART)

Serial Port

RS-232C Serial Cable Internet

Apps

TCP

IP

PPP

Serial Port(UART)

IP

PPP

Serial Port(UART 16550)

Ethernet Driver

Ethernet Card

Apps

TCP

RS-232C Serial Cable Ethernet Cable

Palm Pilot Desktop PC

Internet


PDA

BlueSky Wireless Access Design

Serial Port Internet

Apps

TCP

IP

PPP

IP

PPPEthernet

Driver

Ethernet Card

TCP

Ethernet Cable

Palm Pilot

Internet

WirelessAdapter

WirelessModem

Serial Port

Ethernet Card

AccessPoint

RadioDevice(FSK)

RadioDevice(FSK)

Serial Communication over Serial Port

Palm Pilot

AccessPoint

Telnet

Optional

Radio device is a wireless modem that takes serial stream of bytes as input and modulatesthem over the 915Mhz carrier frequency using FSK modulation.


PDA

PDA

Serial Port

Palm Pilot 1

WirelessAdapter

WirelessModem

Serial Port

Ethernet Card

AccessPoint

Serial Port

Palm Pilot 2

WirelessAdapter

When two palm-pilots transmit at the same time, collisions may occur on the uplink channel. Hence, we need Media Access Control for Uplink.

Downlink Channel(Channel 1)

BlueSky Wireless Channel - DownlinkThere are two wireless physical channelsthat are used between an access point and mobile stations.

1) Downlink channel (channel 1 – f1)2) Uplink channel (channel 2 – f2)

Namely. FDD scheme is used for duplexing.


PDA

PDA

BlueSky Wireless Channel - Uplink

Serial Port

Palm Pilot 1

WirelessAdapter

WirelessModem

Serial Port

Ethernet Card

AccessPoint

Serial Port

Palm Pilot 2

WirelessAdapter


Uplink Channel(Channel 2)

Collision!

Uplink channel is shared betweenmobiles that are in the control of the access point. Since it is sharedcollisions may occur without media access control.


PDA

PDA

BlueSky Wireless Channel Access

Serial Port

Palm Pilot 1

WirelessAdapter

WirelessModem

Serial Port

Ethernet Card

AccessPoint

Serial Port

Palm Pilot 2

WirelessAdapter


The uplink channel is access by using a polling based mediaaccess control protocol.


PDA

Serial Port Internet

Apps

TCP

IP

PPP

IP

PPPEthernet

Driver

Ethernet Card

TCP

Ethernet Cable

Palm Pilot

Internet

WirelessAdapter

WirelessModem

Serial Port

Ethernet Card

AccessPoint

Wireless MAC

RadioDevice(FSK)

Wireless MAC

RadioDevice(FSK)

Serial Communication over Serial Port

Palm Pilot

WirelessAdapter

AccessPoint

Telnet

Optional

BlueSky Wireless Access Design with MAC

Pseudo-Serial Communication over Virtual Port


Wireless Adapter Design

Apps

TCP

IP

PPP

Palm Pilot

UART Driver

Serial Port of PDA (UART)

MACProtocol

PC104 Board

i386 CPU

MS-DOS

RadioTransceiver

(FSK Modulation)

Serial Port (UART1655)

IP PayloadIP Hdtr

IP PayloadIP HdrPPP Hdr CRC

IP PayloadIP HdrPPP Hdr CRCMAC Hdr FCS

1 0 1

0111111011001001

stream of

bytes

stream of

bytes Serial Port

WirelessAdapter


Wireless Adapter – Outside view

Wireless adapter workingprototype (little bit big!!)

Wireless adapter envisionedproduct form factor.


Wireless Adapter – Inside – Development Board

Serial portconnected

to PDA

i386CPU

Flash Diskto store files

(2MB)

RadioTransceiver

Antenna

A/CAdapter

PC-104Board

RSSIPin

Parallel Portconnected to radio transceiver

Serial portConnected

to radiotransceiver

2-4MB RAM


Wireless Adapter – MAC Development Cycle

Physically transfer the flash disks to wirelessadapters (be careful not to break the pins!)

Access Point

Monitor

PC withwindows

• Write MAC protocol software for mobile wireless adapter (using C in Visual C++ environment) in a standalone PC with windows.

• Compile the software for DOS and obtain mac.exe

• Transfer the MAC executable to developmentboard using a floppy (dev. board has a floppydrive).

• At the dev. board, copy the executable from floppy to flash disk of each wireless adapter.

Run the prototypes and test!Dev. Board

FLASH DISK

Repeat 1,2,3,4until Success!

1

2

3

4


What is PC104 Basically a PC with different

form factor (shape and size) Stackable cards

Video cards, ethernet cards, flopply drive, ...

Cards are connected originally with 104 pins.

Cards are much smaller than ISA cards used in PCs.

Suitable for embedded systems. Floppy Disk Drive (optional)

10Base-T Ethernet Card (optional)

VGA Card (optional)

PC-104 Board


RS-232C

modemRS232C cable Telephone line

DTE Device DCE Device

Standard for transmitting serial stream of data over short-distances. - Between two computers in a room - Between a computer and a modem - Between a computer and a device - Between two devices

Defines: - The signal levels to represent bits/bytes - The line types in a cable to transmit/receive data and control signals.

RS232C cable

DTE Device DTE DeviceDTE: Data Terminal EquipmentDCE: Data Commmunication Equipment (Circuit terminating)


Rx FIFO(16 bytes)

Tx FIFO(16 bytes)

RS232 Cable

UART Core

Microprocessor Interface

UART 16550

PPPCOMPUTER

IP

UART Driver

UART: Serial PortInterface

OperatingSystem

Serial PortInterface (UART)

UART: Universal

AsynchronousReceiver Transmitter


DB25 Male Connector DB25 Female Connector

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

118

19

20

21

22

23

24

25

DTR

Tx D

Rx D

RTS

CTS

SD

12

11

10

9

18

7

6

5

4

3

2

1

25

24

23

122

21

20

19

18

17

16

15

14

13

DTR

TxD

Tx D

RTS

CTS

SG

DSR

CD

RI

DSR

CD

TxD: Transmite Data (from DTE to DCE)RxD: Receive Data (from DCE to DTE) RTS: Request to Send (from DTE to DCE)CTS: Clear to Send (from DCE to DTE)DSR: Data Set Ready (from DCE to DTE) DTR: Data Terminal Ready (from DTE to DCE)SD: Signal GroundCD: Carriier Detect (from DCE to DTE)

RS232C Connectors – 25 Pin


1

TxD

RxD

DTR

SG

3

4

5

26

8

9

7

5

3

2

1

49

7

6

8

RxD

TxD

DTR

SG

DSR

RTS

CTS

CTS

RTS

DSR

DB9 Male ConnectorDB9 Female Connector

TxD: Transmite Data (from DTE to DCE)RxD: Receive Data (from DCE to DTE) RTS: Request to Send (from DTE to DCE)CTS: Clear to Send (from DCE to DTE)

DSR: Data Set Ready (from DCE to DTE) DTR: Data Terminal Ready (from DTE to DCE)SD: Signal GroundCD: Carriier Detect (from DCE to DTE)

RS232C Connectors – 9 Pin


0 1 0 0 0 0 0 1 0 1 1

Start bit

7 data bits

Parity bitTwo stop bits-15V

+15V

-3V

+3V

Mark (=1)

Space(=0)

IntermediateRegion

Data byte transmission corresponding to ascii character A (65)

RS232C Data Transmission

LSB MSB

0V


TxD

RxD

RTS

CTS

2

3

4

5

Femaleconnector

TxD

RxD

RTS

CTS

2

3

4

5

DTE DeviceComputer

RxD

TxD

CTS

RTX

2

3

4

5

Null-ModemCable

Femaleconnector

Femaleconnector

DTE DeviceComputer

RxD

TxD

CTS

RTX

2

3

4

5

Maleconnector

DCE DeviceMODEM

DTE DeviceComputer

Connnecting Terminals using RS-232


MAC Protocol

Polling based Works over full-duplex wireless

channel Uplink channel: from mobiles to

access point (shared) Downlink channel: from access

point to mobiles (no concention)

Support sleep modes to save power

In its simplest form, round-robin poll schedule

With appropriate scheduding can support different rates to each mobile

MAC Hdr(8 bytes)

Data (optional)(0-2K bytes)

CRC (or FCS)(2 bytes)

MAC Header Fields:- Temp MAC address: 1 bytes- Length: 2 bytes- MAC start frame delibiator- Type of Frame: POLL, NODATA, DATA, REGISTRATION, etc - Flags

-Sequence No: 1 bit-ACK (1 bit)


MACradio1

radio2MAC

radio3MAC

MACradioAP

full duplex

Ad an ON/OFF switch to each radio and control itusing a MAC protocl

Access Point

Radio Channels over which MAC operates (2 channels)


MAC protocol overview

MACradio1

radio2MAC

radio3MAC

MACradioAP

Access Point

Poll-R1

DATA

Poll-R2

No-DATA

Poll-R3

DATA

radio4MAC

InviteRegister


MAC Protocol Concept - 1

AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

AP-MAC: AP side of the MAC protocolM-MAC: mobile side of MAC protocol

M1

M2

M3

APM1 Data FCS....

Addr Data FCS....

MAC Header Payload CRC

Channel 1

DATA is variable size with some maximum value.



AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M1

M2

M3

AP

APDataFCS ....

Channel 2



AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M1

M2

M3

APM2 FCS....

Channel 1

POLL



AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M1

M2

M3

APAPDataFCS ....

Channel 2



AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M1

M2

M3

APM3 Data FCS....

Channel 1

DATA is variable size with some maximum value.



AP-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M-MAC

RADIO

M1

M2

M3

AP

APFCS ....

NODATA

Channel 2


MAC Registration and change of point of

Attachment.

AP1 AP2

M1 M2 M3 M4 M5M31

2

3

1. M3 moves out of region of AP1. After some threshold time it will detect that is lost connection will start listening to INVITE packets from other access points if there exists any.

2. When it enter to the region of AP2, it will hear an INTIVE from AP2 and will responde with a REGISTRATION REQUEST after some random backoff time. AP2 will reply to REGISTRATİONREQUEST with a REPLY. REPLY will contain a temporary 1 byte MAC address for M3.

3. M3 will receive REPLY and now it is registrated with AP2. 4. Data Communication can resume over AP2. 5. AP1 will delete M3 from its table after some period.

Both AP1 and AP2 are using the same uplink and downlink radio channels. Therefore, they should not overlap.

This problem can be solved by using more channels.

INVITE

REGRPL


ProblemMultiplex traffic (PPP packets) from

multiple PPP interfaces at the MAC layer and send them as MAC payloads to

appropriate mobile devices depending on which PPP interfaces the packets has

came from.

Demultiplex MAC frame payloads to different PPP interfaces depending on from which mobiles the frames came

from (again at the MAC layer)

PPPPPP

InternetWirelessModem

Serial Port

Ethernet Card

AccessPoint

Pseudo-Serial Communication over Virtual Port

BlueSky Access Point Design

IP

PPPEthernet

Driver

Ethernet Card

TCP

Ethernet Cable Internet

Wireless MAC

RadioDevice(FSK)

AccessPoint

Telnet

OptionalRun multiple PPPInterfaces for each

mobile device registered.


BlueSky Access Point Design

Serial Cable

Radio Transceiver

Serial Port

Serial Port

Access Point is Unix Box connected to a radio transceiver over a serial cable. It can run BSDI/OS or Linux.

It may have a monitor connected for debugging purposes.

MAC protocol is implemented as a user level process that talks to the serial port (hence to radio transceiver) on one end and to the PPP interfaces at the other end.

Access point can be configured as IP forwarder to forward the IP packets back and forth between Internet (or LAN) and Wireless Link

Access point terminates the PPP connections from mobile device (namely AP runs a PPP serverfor each mobile that is running a PPP client and that is connected to the AP).

InternetEthernet

Cable

Access Point


UART

Telnet Server Process

Ethernet Card

Network Interfaces

BlueSky Access Point Implementation

UART Driver

Ether0

Ethernet Cable

RadioDevice(FSK)

PPP0 PPP1 PPPn

tty1 tty2 ttynpty1 pty2 ptyn

TCP

/dev/pty1 /dev/pty2 /dev/ptyn /dev/ttya

EthernetDriver

Routing Table IP

MACProtocol

AP MAC Process

Pseudo-terminalSlaves

Pseudo-terminalMasters

Unix Kernel

FCS PPP_H MAC_H

IP Pkt Eth HdrCRC

Frame Coming from Mobile 2 Frame going to LAN

IP PktCRC

PPP_HIP PktCRC

IP Pkt


What is PPP?

PPP is Point-to-point protocol It is a protocol to encapsulate IP datagrams so that they can be

sent over serial lines Serial line transmission is just a stream of bytes. It does not have any

packet boundaries. Connection oriented.

A connection has to be established between PPP peers (PPP client and PPP server) before transmitting data (IP packets most of the time).

PPP functions Framing

Encapsulation of Network Layer packets into PPP frames so that they can be sent over serial lines

Link control protocol To establish, test, and configure data-link connections.

Network control protocol To configure the network layer protocols.


PPP Framing

Flag0x7E

Addr0xFF

Control0x03

Protocol Information CRCFlag0x7E

1 1 1 2 up to 1500 bytes 2 1

0x0021 IP packet

0xc021 LCP Data

0x8021 NCP Data

LCP: Link Control Protocol

NCP: Network Control Protocol

ACP: Authentication Control Protocol

CRC is computed over Addr, Control, Protocol, and Information fields before byte stuffing.

PPP DATA PACKET

PPP CONTROL PACKET

PPP CONTROL PACKET

PPP Frame format (used for both control and data packets)


IP

Why PPP Framing needed?

Serial Port(UART)


Ethernet Driver

Ethernet Card

RS-232C Serial Cable

IP Payload

IP Payload

IP Payload

………………

IP

TCP

APP

Serial PortDriver

Serial PortDriver

Length

Length

Length

IP Packets are sent over serial line without any other encapsulation. Serial line is not error-free. Some bytes can get corrupted. Assume the receiver IP detects the boundaries of IP packets by looking to the length field in the header of IP packets. If the byte(s) that is corrupted carries the length field of the IP packet that is currently transmitted overthe serial line, the the receiving IP layer can not detect the end-of-IP-packet correctly. Hence we will loose synchronization between two ends and no further IP packet can be received correctlyat the receiver side.

Assume we run IP directly over Serial Port without using PPP.


Byte StuffingReplace the occurrence of 0x7e with 0x7d, 0x5eReplace the occurrence of 0x7d with 0x7d, 0x5d

56 99 01 7d 5e 05 7d 5d 17 7d 5d 7d 5e 89

56 99 01 7e 05 7d 17 7d 7e 89

210003ff7e

19 7d

7e

Byte Stuffed Content

Data CRC

Start of Frame

End of Frame

210003ff

19 7d 5d

Hdr

0x7e is the flag byte. 0x7d is the escape byte. Inside the frame, no occurrences of 0x7e after byte stuffing.

0x7e is in hexadecimal. It is equal to 01111110 in binary.


Apps

TCP

IP

PPPClient Side

Serial Port(UART)

IP

PPPServer Side


Ethernet Driver

Ethernet Card

Ethernet Cable

PPPConnection

Establishment

Data Transfer

1)

2)

PPPConnection

Terminationt3)

PPP Functions

Link Establishment

AuthenticationNetwork

ConfigurationData Transfer Termination

PPP Connection Establishment PPP Connection Termination


PPP Connection Establishment

PPP

CLIENT

LCP Packet (CON_REQ)

LCP Packet (CONF_ACKL)

ACP (REQ)

ACP (ACK)

NCP (CONF_REQ)

NCP (CONF_ACK)PPP

SERVER

- Provideincoming MTU-Set auth protocolto be used. Set outgoing MTU

AuthenticateUsing PAP, CHAP

EAP etc.

Provide IPAddress,

DNS Address, etc.

Set IP AddressSet DNS Address

ProvideInfo for

Authentication (uname, password)

-Set outgoing MTU-Provide incoming MTU-Provide which Authprotocol to be used.

1

2

3

EstablishedEstablished


PPP Connection Establishment

After PPP connection establishment A PPP client learns at least:

the IP and DNS addresses that it will use to connect to the Internet

the link MTU (maximum PPP packet size) that is to be exported to the IP layer, so that IP layer fragments IP packets that are larger than the MTU

PPP Connection establishment Takes time! Incurs a lot of control traffic (control packets) over the low

bit-rate serial (wired or wireless) link.


PPP1 PPP2Ethernet

Driver

Ethernet Card

AP Wireless MAC

RadioDevice(FSK)

Access Point

Apps

TCP

IP

PPP

Wireless MAC

RadioDevice(FSK)

Apps

TCP

IP

PPP

Wireless MAC

RadioDevice(FSK)

Mobile A

Mobile B

139.179.120.10(255.255.255.0)

130.179.121.2

130.179.122.2130.179.122.1 130.179.121.1

PPP Connection

PPP Connection

IP139.129.120/24 eth0

139.129.121.2 pp1

139.129.122.2 pp2

RTTable

Our wireless link and PPP


Looking back to our solution

Our solution so far provides Wireless connectivity for multiple mobile devices that are

connected to a single access point. By use of PPP, mobile devices can run IP and related

applications and access point can act as a forwarder. We may have more than one access point installed in a

target region. We will mobile connected to some access point.

However, the solution so far does not provide seamless mobility between access points, since PPP connection will break upon change of access point and higher layer protocols and applications will be disturbed.


PPP1Ethernet

Driver

Ethernet Card

AP Wireless MAC

Radio

Apps

TCP

IP

PPP

Wireless MAC

Radio

Mobile A

139.179.120.10(255.255.255.0)

130.179.121.2 130.179.121.1

IP

139.129.120/24 eth0

139.129.121.2 pp1

RT Table

Apps

TCP

IP

PPP

Wireless MAC

Radio

Mobile A

130.179.131.2PPP1

Ethernet Driver

Ethernet Card

AP Wireless MAC

Radio

139.179.130.20(255.255.255.0)

130.179.131.1

IP

139.129.130/24 eth0

139.129.131.2 pp1

RT Table

Router

Access Point A

Access Point B

carrier detection

MAC level registration

PPP Connection

carrier detection

MAC level registration

PPP Connection

moves

Data Flow

Mobile’s IP address changes!


BlueSky’s Approach

Do not terminate PPP at the access point. Means: do not run PPP server at the access point.

Run PPP at a backend server. Tunnel PPP traffic from access points to the

backend server. Establish PPP once Redirect PPP traffic to a new tunnel when

point of access changes.


Concept

AP1 AP2

M1 M2 M3 M4 M5M3

PBS

PPP Backend Server (PBS)

PPP

PPP PPP

Eth

IP

INTERNET

Tunnel 1Tunnel 2 (PPP/UDP/IP/LAN)

PPP Connection

Data Flow

Mobile’s IP Address remains same.

139.179.120.2 139.179.120.2

139.179.120.1

LAN

LANLAN


IPWireless

MAC

RadioDevice(FSK)

UDP

Ethernet

Apps

TCP

IP

PPP

Wireless MAC

RadioDevice(FSK)

IP

UDP

Ethernet

PPP

IP

Tunnel

TunnelAgent

TunnelAgent

Palm Pilot

Access Point

PPP Backend Server

Router

IP Pyld IP H

IP Pyld IP H PPP_H

IP Pyld IP H PPP_HCRCFCS MAC_H

IP Pyld IP H PPP_HCRC TUN_H

IP Pyld IP Hdr PPP_HCRC

IP Pyld IP Hdr PPP_HCRC TUN_H

IP Pyld IP H PPP_HCRC TUN_H UDP_H IP_H

IP Pyld IP H

CRC

IP Pyld IP H PPP_HCRC

Protocol Architecture


Unix Kernel

BlueSky New Access Point Implementation

/dev/ttya

MACProtocol

AP_MAC/Tunnel Process

Tunnel Protocol

UDP socket

FCS PPP_HIP PktCRC

PPP_HIP PktCRC

PPP_HCRC TUN_HIP PktMAC_H

LANWireless channel Radio

Device(FSK)

UART

UART Driver

UDP

Ethernet Card

Ethernet Driver

IP


Network Interfaces

BlueSky PPP Backend Server Implementation

PPP0 PPP1 PPPn

tty1 tty2 ttynpty1 pty2 ptyn

UDP

/dev/pty1 /dev/pty2 /dev/ptyn

TunnelProtocol

Pseudo-terminalSlaves

Pseudo-terminalMasters

Frame going to LAN

UDP socket

Routing Table

PPP_H CRCTUN_H IP PktPPP_H CRCIP Pkt

IP Pkt

PPP_H CRCTUN_H IP PktUDP_H

PPP_HCRC IP Pkt

Ethernet Card

EthernetInterface

EthernetDriver

From Access Point

To Internet

Common Data path

Tunnel Process


Advantages of terminating PPP at the backend server and BlueSky in general Authentication is easier.

Password files can be kept at a central location (PBS) Otherwise they should be replicated in each access point.

PPP connection is established once for data communication It is not terminated while changing point of attachment. Only terminated when mobile no longer wants to access the network IP address remains same although point of access changes.

IP layers is unaware of mobility (hence all other higher layers: TCP, UDP, Aplications)

Can support fast handoffs (PPP connection establishment takes time). Is more bandwidth efficient for the resource scarce wireless access link.

Total seamless mobility support Mobility can be supported in this way for other network layer protocols

other than IP such as IPX and Appletalk. No need to modify mobile devices hardware and software.

No need to modify different OS stacks for PDAs.


Limitations of terminating PPP at the backend server and BlueSky in general.

Solutions is restricted with PPP as the data link layer.

All traffic has to go through PPP backend server This can be optimized by parsing PPP packets at the access

point and looking to the destination IP address The bandwidth of the tunnel path (10Mbps) is much much

higher than the bandwidth of the wireless link (150 Kbps) Packet delays are negligible over the wired links.

Running PPP between IP and packet oriented MAC layer introduces:

Extra framing (one at PPP layer, one at the MAC layer) Extra connection time: MAC registration + PPP connection

establishment.


BlueSky Summary

Wireless Access Shared 150 Kbps bandwidth FSK modulation at 915MHz 10m range Full duplex channel (FDD duplexing) Polling based access-point-coordinated MAC protocol

Mobility Solution at the data-link layer Works for PPP and various network protocols: IP, IPX,

AppleTalk Roaming in a single administrative domain.


BlueSky versus Bluetooth

BlueSky BlueToothDeveloped by a small group of people at IBM in 1998.

Developed by a consortium consisting of 5 big companies (IBM, Intel, Toshiba, Ericsson, Nokia) and more than 500 adaptor companies. Started in May 1998.

10m range 10m range

FSK modulation GFSK modulation

915 MHz operating frequency 2.4 GHz operating frequency

FDD duplexing TDD duplexing

Access point coordinated polling based MAC (no strict time slotting)

Master coordinated polling based MAC based on strict time slotting.

150 Kbps shared bandwidth (no limit on devices other than performance).

1Mbps shared bandwidth (at most 8 devices: 1 master, 7 slaves)

Complete networking solution. Does not define exactly how IP can be run over it.

Complete mobility solution. Does not define a mobility solution.

cs 515 © İbrahim körpeoğlu1 bluesky: a new indoor wireless access network and mobility solution...

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