ASSI , MULTIPLE ACCESS

ASSI Online

Number 1, August 1999

MULTIPLE ACCESS IN MOBILE SATELLITE COMMUNICATION

5.0. CONCLUSION

Satellite mobile communication capacities for CDMA, FDMA and TDMA/FDMA have been analyzed for an L/C-band system covering Asia. For the particular mobile satellite system under discussion and for the particular antenna configurations, both CDMA and FDMA offer similar performance, FDMA yielding slightly higher channel capacities at the design point and CDMA being slightly better at higher EIRP levels. As the mobile system grows and the antenna beam size decreases, CDMA appears to be a very efficient system, because it is not limited by L-band bandwidth constraints. However CDMA is wasteful in feederlink bandwidth, and the choice of a multiple access system must take all parameters into consideration, such as oscillator stability, interference rejection, system complexity etc. as well as system cost before deciding on a particular multiple access system.

TABLE III - Link Analysis, Forward Link

Multiple Access Type CDMA FDMA TDMA / FDMA

Number of Beams 140 140 140

Beams / Clusters 4 7 7

Number of Channels 12,800 13,200 12,800

Forward Feeder up-link

Frequency, GHz 6.4 6.4 6.4

Number of channels/carriers 1 1 32

Bit rate per channel, kb/s 4.8 4.8 4.8

Bit rate per carrier, kb/s 1576 10 270

FEC Rate 1/3 1/2 3/4

Transmitter e.i.r.p./carrier, dBW 35 35 50

Free space loss, dB -200 -200 -200

Propagation loss (rain, sys margin, pointing loss), dB -2 -2 -2

Receive antenna gain, dB 25 25 25

Receive carrier power, dBW -142 -142 -127

Carrier bandwidth, dBHz 59.5 37.8 51.3

Noise temperature, dBK 27 27 27

Noise power, dBW -142.1 -163.8 -150.3

(C/N)u, thermal, dB -0.1 21.8 23.3

Number of users per spread bandwidth 88

(C/I), dB (NPR = 20 dB) 4.5 24 24

( C / (N+I) ), up-link,dB -1.4 19.6 20.6

Forward Mobile Down-Link

Frequency, MHz 1550 1550 1550

Number of carriers 12,800 15,000 400

AERP, dBW at NPR = 13 dB 72 72 72

Number of carriers, dB -41 -41.2 -26

Voice activation, dB 4 4 4

Power control advantage, dB, (estimate) 2.5 2.5 2.5

E.I.R.P./carrier, dBW 37.5 36.7 52.5

Free space loss, dB -187.5 -187.5 -187.5

Pointing, atmosphere loss, dB -0.1 -0.1 -0.1

Fading margin, dB -10 -10 -10

Receive antenna gain, dB 1 1 1

Receive carrier power, dBW -159.1 -159.3 -144.1

Bandwidth, dBHz 59.5 37.8 51.3

Noise temperature, dBK 26 26 26

Noise power, dBW -143.1 -164.8 -151.3

(C/N)d, thermal, dB -16 5.5 7.2

(C/N)si, sidelobe, dB -4.5 20.3 20.3

(C/Im), dB -0.5 19 27.5

(C/N)ADJ, dB 0.5 20 20

(C/N)q, dB 44.4 44.2 59.4

Number of users per spread bandwidth 88

(C/I)self, dB -15.3

(C (N+I) ) total, downlink, dB -19 5.3 6.8

Forward Total Link

(C/ (N+I) ) forward total, dB -19.1 5.2 6.7

(C/ (No+Io) ) forward per carrier, dBHz 40.4 43 58

(C/ (No+Io) ) per voice channel, dBHz 40.4 43 43

Bit rate, dBHz 36.8 6.2 36.8

(Eb/ (No+Io) ) of channel, dB 3.6 6.2 6.2

(Eb/ (N+I) ), system required, dB 3.2 5 6

(Eb/No) x X required during fading, dB 3.2 6 6

Margin, dB 0.4 0.2 0

TABLE IV - Link Analysis, Return Link

Type Multiple Access CDMA FDMA TDMA/FDMA

Number of Beams 140 140 140

Beams / Clusters 4 7 7

Number of channels 12,800 13,200 12,800

Return up-link

Frequency, MHz 1600 1600 1600

Bit rate per carrier, kb/s 4.8 4.8 6.8

Channel bandwidth, kHz 900 10 34

Uplink E.I.R.P. dBW -1 -1 8

Free space loss, dB -188 -188 -188

Fading margin, dB -10 -10 -10

Receive antenna gain, dB 42.5 42.5 42.5

Polarization and atmosphere loss, dB -0.5 -0.5 -0.5

Receive carrier power, dBW -156.5 -156.5 -147.5

Bandwidth, dBHz 59.5 37.8 45.3

Noise temperature, dBK 27 27 27

Noise power, dBW -142.1 -163.8 -156.3

(C/N)u, dB -14.4 7.3 8.8

(C/I)sidelobe, dB -4.6 20.3 20.3

(C/N-1), dB (self-interference) -15.6

(C/N)u, total, dB -18.2 7.1 8.4

Signal share, % 0.66 0.83 0.87

Return down-link

Frequency, GHz 3.6 3.6 3.6

Number of carriers, dB 12,000 13,200 1600

Channels per carrier 1 1 8

Bit rate per carrier, kbps 4.8 10 68

EIRP, dBw 46 46 46

Back-off, dB -3 -3 -3

Signal Share -1.8 -0.8 -0.6

Total e.i.r.p., dBW 41.2 42.2 43

Number of carriers, dB -41 -41.2 -32

Voice activation, dB 4 4 4

Power control advantage, dB -4 -4 -4

E.I.R.P./carrier, dBW 0.2 1 10.4

Free space loss, d -195 -195 -195

Fading margin, dB -1.1 -1.1 -1.1

Receive antenna gain, dB 55 55 55

Receive acarrier power, dBW -140.9 -140.1 -130.7

Bandwidth, dBHz 59.5 37.8 45.3

Noise temperature, dBK 21 -21 21

Noise power, dBW -148 -169.8 -162.3

(C/N)d, thermal, dB 7.1 29.7 31.6

(C/Im), dB -2.5 17 17

(C/N)ADJ, dB 0.5 20 20

(C/N)q, dB 23 22.8 32

(C/N)d, total, dB -4.3 13.5 15.2

Total return link

(C/N)total, dB -18 6.2 7.6

(C/No+Io) per carrier, dBHz 61.5 44 52.9

(C/No+Io) per channel, dD 41.5 44 43.9

Bitrate, dBHz 36.8 36.8 36.8

(Eb/No), dB 4.7 7.2 7.1

(Eb/No) x X, required 3.2 6 6

Margin, dB 1.5 1.2 1.1

REFERENCES

Multilateral L-band Meeting 14 - 18 September 1998
"CDMA vs. FDMA Channel Capacity in Mobile Satellite Communication", Klaus G. Johannsen, International Journal of Satellite Communication, Vol. 6, 1988.
"Mobile P-Service Satellite System Comparison", Klaus G. Johannsen, IJSC, 1995
"The Asia Cellular Satellite System", Stuart C. Taylor & Adi R. Adiwoso, American Institute of Aeronautics and Astronautics (AIAA), 1996

Fig.1 Carrier and IM noise spectra in CDMA
Fig 2 Distribution of signals and IM noise products over coverage area B in CDMA
Fig 3 (a) Circular and (b) square beam arrays
Fig.4 Four and Seven beam clusters. Same number indicates frequency reuse of same frequency
Fig.5 CDMA channel capacity VS spot beam EIRP for a 140 spot beam antenna system, Forward link, 4.8 kbps

1 beam cluster, Rate 1/2, Eb/No = 5 dB
4 beam cluster, Rate 1/2, Eb/No = 5 dB
1 beam cluster, Rate 1/3, Eb/No = 3.2 dB
4 beam cluster, Rate 1/3, Eb/No = 3.2 dB

Fig.6 Channel capacity of the return link CDMA, B/b = 140 beams, 4.8 kbps,

1 beam cluster, Rate 1/2, Eb/No = 5 dB
4 beam cluster, Rate 1/2, Eb/No = 5 dB
1 beam cluster, Rate 1/3, Eb/No = 3.2 dB
4 beam cluster, Rate 1/3, Eb/No = 3.2 dB

Fig.7 FDMA and TDMA/FDMA Channel Capacity VS EIRP for 4.8 kbps voice

7 beam cluster, Rate 1/2, FDMA
4 beam cluster, Rate 1/2, FDMA
7 beam cluster, Rate 3/4, TDMA/FDMA
4 beam cluster, Rate 3/4, TDMA/FDMA

Fig.8 FDMA and TDMA/FDMA Returnlink Channel Capacity, Power Limited operation

FDMA, 7 beam cluster, Rate 1/2, Eb/No = 6 dB
FDMA, 4 beam cluster, Rate 1/2, Eb/No = 6 dB
TDMA/FDMA, 7 beam cluster, Rate 3/4, Eb/No = 6 dB
TDMA/FDMA, 4 beam cluster, Rate 3/4, Eb/No = 6 dB

Fig. 9 Multiple Access Channel Capacity VS Spot beam EIRP for 140 Beams, Forward Link, Bitrate = 4.8 kbps

FDMA, 4 beam cluster, Rate 1/2, Eb/No = 5.5 dB
CDMA, 4 beam cluster, Rate 1/2, Eb/No = 5 dB
TDMA/FDMA, 4 beam cluster, Rate 3/4, Eb/No = 6 dB
CDMA, 4 beam cluster, Rate 1/3, Eb/No = 3.2 dB

Fig. 10 Mobile Multiple Access Comparison Channel Capacity vs Number of Spot beams 4.8 kbps per channel bit rate

By: Susi Andriani, Agus B. Tjahjono, Hendri Lucky, Cessy Karina, Klaus G. Johannsen PSN, ASSI (Asosiasi Satelit Indonesia)

COVER

TABLE III - Link Analysis, Forward Link
Multiple Access Type		CDMA		FDMA	TDMA / FDMA
Number of Beams		140		140	140
Beams / Clusters		4		7	7
Number of Channels		12,800		13,200	12,800
Forward Feeder up-link
Frequency, GHz		6.4		6.4	6.4
Number of channels/carriers		1		1	32
Bit rate per channel, kb/s		4.8		4.8	4.8
Bit rate per carrier, kb/s		1576		10	270
FEC Rate		1/3		1/2	3/4
Transmitter e.i.r.p./carrier, dBW		35		35	50
Free space loss, dB		-200		-200	-200
Propagation loss (rain, sys margin, pointing loss), dB		-2		-2	-2
Receive antenna gain, dB		25		25	25
Receive carrier power, dBW		-142		-142	-127
Carrier bandwidth, dBHz		59.5		37.8	51.3
Noise temperature, dBK		27		27	27
Noise power, dBW		-142.1		-163.8	-150.3
(C/N)u, thermal, dB		-0.1		21.8	23.3
Number of users per spread bandwidth		88
(C/I), dB (NPR = 20 dB)		4.5		24	24
( C / (N+I) ), up-link,dB		-1.4		19.6	20.6
Forward Mobile Down-Link
Frequency, MHz		1550		1550	1550
Number of carriers		12,800		15,000	400
AERP, dBW at NPR = 13 dB		72		72	72
Number of carriers, dB		-41		-41.2	-26
Voice activation, dB		4		4	4
Power control advantage, dB, (estimate)		2.5		2.5	2.5
E.I.R.P./carrier, dBW		37.5		36.7	52.5
Free space loss, dB		-187.5		-187.5	-187.5
Pointing, atmosphere loss, dB		-0.1		-0.1	-0.1
Fading margin, dB		-10		-10	-10
Receive antenna gain, dB		1		1	1
Receive carrier power, dBW		-159.1		-159.3	-144.1
Bandwidth, dBHz		59.5		37.8	51.3
Noise temperature, dBK		26		26	26
Noise power, dBW		-143.1		-164.8	-151.3
(C/N)d, thermal, dB		-16		5.5	7.2
(C/N)si, sidelobe, dB		-4.5		20.3	20.3
(C/Im), dB		-0.5		19	27.5
(C/N)ADJ, dB		0.5		20	20
(C/N)q, dB		44.4		44.2	59.4
Number of users per spread bandwidth		88
(C/I)self, dB		-15.3
(C (N+I) ) total, downlink, dB		-19		5.3	6.8

Forward Total Link
(C/ (N+I) ) forward total, dB		-19.1		5.2	6.7
(C/ (No+Io) ) forward per carrier, dBHz		40.4		43	58
(C/ (No+Io) ) per voice channel, dBHz		40.4		43	43
Bit rate, dBHz		36.8		6.2	36.8
(Eb/ (No+Io) ) of channel, dB		3.6		6.2	6.2
(Eb/ (N+I) ), system required, dB		3.2		5	6
(Eb/No) x X required during fading, dB		3.2		6	6
Margin, dB		0.4		0.2	0
TABLE IV - Link Analysis, Return Link
Type Multiple Access	CDMA		FDMA			TDMA/FDMA
Number of Beams	140		140			140
Beams / Clusters	4		7			7
Number of channels	12,800		13,200			12,800

Return up-link
Frequency, MHz	1600		1600			1600
Bit rate per carrier, kb/s	4.8		4.8			6.8
Channel bandwidth, kHz	900		10			34
Uplink E.I.R.P. dBW	-1		-1			8
Free space loss, dB	-188		-188			-188
Fading margin, dB	-10		-10			-10
Receive antenna gain, dB	42.5		42.5			42.5
Polarization and atmosphere loss, dB	-0.5		-0.5			-0.5
Receive carrier power, dBW	-156.5		-156.5			-147.5
Bandwidth, dBHz	59.5		37.8			45.3
Noise temperature, dBK	27		27			27
Noise power, dBW	-142.1		-163.8			-156.3
(C/N)u, dB	-14.4		7.3			8.8
(C/I)sidelobe, dB	-4.6		20.3			20.3
(C/N-1), dB (self-interference)	-15.6
(C/N)u, total, dB	-18.2		7.1			8.4
Signal share, %	0.66		0.83			0.87

Return down-link
Frequency, GHz	3.6		3.6			3.6
Number of carriers, dB	12,000		13,200			1600
Channels per carrier	1		1			8
Bit rate per carrier, kbps	4.8		10			68
EIRP, dBw	46		46			46
Back-off, dB	-3		-3			-3
Signal Share	-1.8		-0.8			-0.6
Total e.i.r.p., dBW	41.2		42.2			43
Number of carriers, dB	-41		-41.2			-32
Voice activation, dB	4		4			4
Power control advantage, dB	-4		-4			-4
E.I.R.P./carrier, dBW	0.2		1			10.4
Free space loss, d	-195		-195			-195
Fading margin, dB	-1.1		-1.1			-1.1
Receive antenna gain, dB	55		55			55
Receive acarrier power, dBW	-140.9		-140.1			-130.7
Bandwidth, dBHz	59.5		37.8			45.3
Noise temperature, dBK	21		-21			21
Noise power, dBW	-148		-169.8			-162.3
(C/N)d, thermal, dB	7.1		29.7			31.6
(C/Im), dB	-2.5		17			17
(C/N)ADJ, dB	0.5		20			20
(C/N)q, dB	23		22.8			32
(C/N)d, total, dB	-4.3		13.5			15.2

Total return link
(C/N)total, dB	-18		6.2			7.6
(C/No+Io) per carrier, dBHz	61.5		44			52.9
(C/No+Io) per channel, dD	41.5		44			43.9
Bitrate, dBHz	36.8		36.8			36.8
(Eb/No), dB	4.7		7.2			7.1
(Eb/No) x X, required	3.2		6			6
Margin, dB	1.5		1.2			1.1