How big is a passive picocell

1
How big is a passive picocell ?

• David Wake
• BT Laboratories
• UK

2
introduction

• work is based on results of EURESCOM Project P816
• evaluation of technology for hybrid optical -
  radio networks
• passive picocell is one potential technology
  identified in this project
• novel concept using unpowered remote optical -
  radio transceiver
• important question what is the radio range
  without amplifiers ?
• i.e. how big is a passive picocell ?

3
outline

• what is a passive picocell ?
• how does it work ?
• what are the benefits ?
• what are the potential applications ?
• how big is a passive picocell ?
• second generation cellular (DCS1800)
• third generation cellular (UMTS)

4
what is a passive picocell ?

• a small radio cell formed using a fibre-supported
  antenna unit that is
• small, light and unpowered
• multiband capable
• upgradable and reconfigurable from central
  location

5
how does it work ?

• electroabsorption modulator transceiver
• acts as photodiode for downlink
• acts as modulator for uplink
• connected directly to antenna
• can operate without bias voltage

CENTRAL SITE
REMOTE SITE
laser
downlink fibre
E A M
photo diode
uplink fibre
6
demonstration system
PSTN
optical source
DECT base unit
picocell
multiplexer circulator
dual fibre link
radio LAN access point
optical receiver
Ethernet
central site
passive base station
passive optical transceiver
7
what are the benefits ?

• simple installation
• low maintenance
• multiband, multisystem
• easily reconfigured and upgraded
• simple dynamic radio resource control
• low total network cost ?

8
what are the potential applications ?

• indoor and outdoor
• public and private
• cellular, cordless, fixed radio access, wireless
  LAN
• picocells, microcells
• urban, in-building
• offices, factories, warehouses, railway stations,
  airports, sports stadia, ...

9
how big is a passive picocell ?

• relies only on rf power available after
  photodetector
• optical system parameters used to compute power
• cell size depends on propagation environment and
  sensitivity of terminal
• two systems analysed (DCS1800 and UMTS)
• two propagation environments considered
• open, line-of-sight (power reduces with square of
  distance)
• cluttered, non line-of-sight (power reduces with
  cube of distance)

10
important optical parameters

• EAM responsivity 0.3 A/W
• EAM efficiency 0.5 /V
• EAM insertion loss 7 dB
• photodiode responsivity 1 A/W
• fibre insertion loss 3 dB
• source optical power main variable

11
important radio parameters

• DCS1800 UMTS
• terminal transmit power 20 dBm 20 dBm
• terminal sensitivity -100 dBm -110 dBm
• optical modulation depth 20 pc 50 pc
• antenna gain 8.5 dB 8.5 dB
• fade margin 10 dB 10 dB
• path loss exponent secondary variable

12
cell size equations
13
results - DCS1800
14
results - UMTS
15
conclusions

• emerging new technology for picocells
• important benefits
• installation, maintenance, upgrading,
  reconfiguring, dynamic resource allocation
• how big is the picocell ?
• DCS1800 52m LOS 14m NLOS
• UMTS 374m LOS 52m NLOS
• powered version for larger range ?
• next major question - cost