BBPF Technique for Transmitter Noise Reduction in a Site-Shared Wireless Network and Its Performance Evaluation Using NCP

Journal of Wireless Networking and Communications 2015, 5(2): 49-59
DOI: 10.5923/j.jwnc.20150502.01
BBPF Technique for Transmitter Noise Reduction in a
Site-Shared Wireless Network and Its Performance
Evaluation Using NCP
Nosiri O. C.*
, Ononiwu G. C., Ekwueme E. U., Akande A. O.
Electrical Electronic Engineering, Federal University of Technology, Owerri, Nigeria
Abstract Infrastructure sharing approach has been adopted by wireless communication service providers as a panacea to
reduce the huge cost involved in building new cell sites. The paper was designed at providing adequate solution to mitigate
the transmitter noise effect involving downlink frequency of CDMA-2000 in the frequency range (1960-1990MHz) and
uplink WCDMA in the frequency range (1920-1980MHz) in a co-located network. The paper further introduced the
application of a digital BBPF as a technique to attenuate the significant effects of the transmitter noise. BBPF technique was
considered more suitable among the Infinite Impulse Response (IIR) filters such as Chebyshev I and II, Elliptic and Bessel
filters due to its attributes to least amount of phase distortion. Practical measurements conducted in two difference scenarios
demonstrated the significant effects of the downlink frequency of CDMA2000 on the uplink frequency of the WCDMA
network. A 52dB rejection at 5MHz guard band offset from the low side edge of the pass band was obtained as the undesired
signal magnitude required to be attenuated. Conversely, an NCP criterion was introduced to evaluate the various performance
characteristics at 52dB which gave rise to amplitude imbalance of 0.03dB, phase error of 0.140
and time delay mismatch of
0.07ns respectively. The values obtained in the study showed that the magnitude specification at 52dB rejection can to a
larger extent attenuate the sideband noise components present in the WCDMA receiver front end.
Keywords Transmitter noise, WCDMA, CDMA2000, BBPF, NCP
1. Introduction
With the advancement in wireless communication
technology and the rapid increase in the demand for mobile
systems has necessitated network operators to build more
cell sites to provide coverage to some geographic regions
where there are no wireless networks, to cover areas where
existing signals are weak especially in the rural areas and to
support a larger number of customers to meet the higher
speed requirements of emerging technologies [1]. The need
to meet the requirements has led to the proliferation of new
cell towers which are capital intensive. The solution to the
obvious challenge was the introduction of infrastructure
sharing strategy by the International Telecommunication
Union (ITU), where all the wireless network regulatory
bodies globally are advised to adopt the reform. This was
driven by the need to [2, 3].
● Reduce the incessant proliferation of
telecommunication towers
* Corresponding author:
buchinosiri@gmail.com (Nosiri O. C.)
Published online at http://journal.sapub.org/jwnc
Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved
● Share more networks on the same tower as a means
to optimize savings and efficient utilization of the
available resources
● Promote fair competition through equal access
granted to the installations and facilities of
operators on mutually agreed terms.
● Stimulate easy migration to new technologies and
the deployment of mobile broadband.
● Improve the market penetration and profit margins
for telecom operators in the emerging markets
The initiative was primarily focused to generate economic
growth with improved network quality and help developing
and developed countries to meet the objectives of the World
Summit on the Information Society and the Millennium
Development Goals established (ISMDG) by the United
Nations [4].
Cell site sharing reform was introduced in Nigeria by the
Nigerian Communication Commission (NCC). Sequel to the
benefits and developments, operators such as MTN, Etisalat,
Globalcom, Visaphone and Airtel seeking to expand their
network services by building new cell sites are regulated and
managed by the NCC licensed service vendors such as the
IHS Plc, Swap Technologies, MTI and Helios Towers [5, 6].
Telecommunications infrastructure sharing for operators

50 Nosiri O. C. et al.: BBPF Technique for Transmitter Noise Reduction in a Site-Shared
Wireless Network and Its Performance Evaluation Using NCP
primarily consists of: [7, 4]
a) Active infrastructure sharing (such as spectrum,
switches, antennae, transceivers and microwave
equipment).
b) Passive infrastructure sharing (such as towers, BTS
shelters, power supply, generators, batteries and
air-conditioners) and
c) Operators Backhaul sharing (core network elements
such as switching centers, GPRS service nodes,
transmission equipment and all links connecting
elements of the core network).
Currently, the most commonly shared infrastructure
among operators is passive infrastructure, because it is easier
to contract its set-up and maintenance. Two co-located
network operators investigated in the study are MTN
(WCDMA) and Visaphone (CDMA2000). The frequency
spectrum allocation used by Nigerian network operators for
WCDMA and CDMA2000 are shown in Table 1. A vital
consideration when analyzing a co-located network is to
establish if the frequencies of the networks are adjacent to
each other, overlap or have close ranges.
Table 1. Frequency spectrum for CDMA-2000 AND WCDMA [8]
Wireless
access
technology
Mobile station
transmitter
(MHz) (Uplink)
Base station
Transmitter (MHz)
(downlink)
Duplex
separation
(MHz)
CDMA
2000
1850-1910 1960-1990 80
WCDMA 1920-1980 2110-2170 190
The frequency band allocation for CDMA 2000 downlink
as shown in Table 1 is between 1960-1990MHz and that of
WCDMA uplink is between 1920-1980MHz. This showed
that the CDMA2000 transmitter (Tx) frequency band
overlaps with the WCDMA receiver (Rx) frequency band
by 20MHz, therefore, the two networks will interfere in a
co-located setting. On the other hand there is wide
frequency band isolation between WCDMA transmitting
frequency and CDMA2000 receiving frequency; hence,
there is no possibility of the two systems interfering.
The paper predominantly examined the effects of the
transmitter noise radiation from the downlink frequency of
CDMA2000 network on the uplink frequency of WCDMA
receiver system in a co-located platform and proffered
industrial solution to mitigate the noise through the
deployment of Butterworth Band Pass Filter (BBPF)
technique and also evaluated the magnitude design
specification performance using Noise Cancellation
Performance (NCP) criteria.
2. Literature Review
Author of [9] characterized transmitter and receiver
performance based on lab tests conducted on commercial
equipment for both UMTS 900 and GSM 900MHz
terminals and base stations. The impact of GSM Mobile
Stations (MS) and UMTS node B and user end with GSM
BTS on receiver performance were assessed. The result
obtained showed that the limiting factor was the
interference caused by the GSM MS to the UMTS Node B
and that as little as 4.2MHz of GSM spectrum can be
cleared and allocated to the UMTS carrier with satisfactory
system performance. The paper actually considered the
major steps required to address the issue of transmitter
noise interference but failed to analyze the various levels of
percentage capacity degradation and noise rise as the
interfering power increases. This is significant because it
identified percentage capacity loss relative to the rise in
interfering power.
Another author of [10] developed an interference
reduction mechanism based on physical optimization of
antenna system that could be understood as a physical
symmetry rotation in the space of parameters such as tilt
and azimuth control system. The method acts only on some
parameters of the system such as tilt and Azimuth. This
gave a solution to independently reduce the interference
effects on the distance between the base stations. Only
physical optimization of antenna isolation is not adequate
for proper attenuation of transmitter noise. Additional
mitigation techniques are necessary for optimal
performance.
The authors of [11] investigated the effects of adjacent
channel interference radiated by CDMA2000 on the
WCDMA system uplink and downlink scheme in Indonesia.
Several scenarios and calculation models to evaluate the
impact on the uplink and downlink scheme were deployed.
Their work emphasized on the computations and simulation
performance in one cell scenario, where one WCDMA base
station, referred to 3G Node B, serving greater number of
WCDMA mobile stations (Ms). Two calculations were made
on the uplink by varying the distance, guard band frequency
and number of CDMA 2000 MS. It was designed by setting
CDMA2000 MS as source of interfere. The first calculation
was to obtain the minimum allowed received power at
WCDMA BS while the second calculation provided the
capacity degradation. In the downlink scenario,
measurements were conducted to obtain the capacity
degradation of WCDMA MS due to the presence of CDMA
2000 BS. Simulation analysis was also developed in one cell
scenario where one WCDMA BS served numbers of its
user’s. The WCDMA downlink simulation was actualized by
distributing the number of WCDMA MS randomly in one
cell, defining the position of one CDMA 2000 BS and its
distance to the WCDMA BS and calculating the pathloss
value for each WCDMA MS towards WCDMA BS and
CDMA2000 BS. Others include: calculating the total
transmission power of WCDMA BS, calculating the
allocated transmission power for every WCDMA MS before
the presence of the CDMA2000 BS and calculating the
interference power generated by CDMA2000 BS for each
pathloss value and the Signal to Interference Ratio (SIR)
value for every WCDMA MS after the presence of CDMA
2000 BS.

Journal of Wireless Networking and Communications 2015, 5(2): 49-59 51
The work of [11], demonstrated the co-existence
performance effect of CDMA2000 and WCDMA network. It
emphasized on the adjacent channel interference of
CDMA2000 MS on the WCDMA BS and CDMA BS on
WCDMA MS. The authors were able to establish the
significant reduction effects on the SIR and capacity loss of
the WCDMA network due to the interference from CDMA
2000 BS which reduces the number of user equipment. The
authors developed good analysis but principally accentuated
on the significant effects of interference on the networks of
interest. On the other hand, no further work or proposal was
put in place on the need towards developing adequate
mitigation technique (s) to reduce the interference issue,
rather they considered increasing the distance and guard
band frequencies which may have significant effect
especially on the coverage radius and usage bandwidth.
The authors of [12] addressed the key characteristics of
interference in wireless networks and the effect of
interference from Code Division Multiple Access (CDMA
2000) base station on the Wideband-Code Division Multiple
Access (WCDMA) network. The analysis of the coexistence
CDMA2000 with WCDMA operating in the same
geographic area was established using deterministic
computations by considering a worst-case scenario. The
authors also considered that a 5MHz protection band
between PCS and UMTS band was necessary. They
suggested the application of filter of realistic complexity and
cost to be installed at the CDMA BS transmitter path with 60
dB attenuation and the required antenna-to-antenna isolation
to be 58 dB. They also recommended that vertical separation
of antennas could lead to lesser values for antenna gains and
reduces the burden on the required isolation. The authors
failed to evaluate the level of interference caused by the
CDMA 2000 transmitter on the WCDMA receiver front end
and the level of the receiver sensitivity degradation with the
corresponding noise rise. On the other hand, no mitigation
technique was developed. To obtain a good result in such
coexistence scenario, it is strongly recommended to
characterize the environment; this will give a better
evaluation performance since the environment is a major
consideration factor for interference analysis.
3. Methodology
The communication channel considered in this study was
the Radio Frequency (RF) path present from the transmit
power amplifier to the receive antenna of the co-located
networks. The article proposed the application of BBPF as a
mitigation technique. The application of BBPF technique
requires a priori knowledge of both the signal and noise
characteristics. The method was based on knowing the
interference properties and knowing the parameters of the
radio devices. The interference leakage of the CDMA2000
Tx signal power on WCDMA Rx signal was investigated.
The approach was considered using two scenarios; the test
network was set up in the eastern part of the country. The
first scenario involved an unco-located WCDMA network
while the second scenario involved a co-located network
comprising of CDMA 2000 and WCDMA. The technique
constituted the applications of empirical analysis.
Scenario one involved the measurements of the reference
received signal strength and the evaluation of the system
noise floor level, system capacity and the carrier to
interference ratio for the unco-located networks while
scenario two considered the measurements of the received
signal power, Effective Radiated Power (ERP) and the
mathematical evaluation of the interfering signal power.
Others include calculating the noise floor level, Carrier to
Interference (C/I) ratio, system capacity and percentage C/I
ratio degradation respectively for the co-located networks.
The measurements were conducted in two seasonal periods:
dry and rainy season, to obtain the best possible average
received signal power and effective radiated power for the
system design.
A Huawei software M2000 Service Maintenance System
CBSS installed in a laptop was the software used to conduct
the measurements. The software provided the window where
the sites to be measured were selected within the sector and
the carrier. The M2000 software provided a centralized
network management and an integrated topology window
through which users can create and manage the topology
view of the entire network. The topology view displayed the
networking status, geographical locations of devices, link
status between devices, and connection status between
devices and the M2000.
3.1. Mathematical Procedure
The model used to obtain the Noise Figure (NF) is given in
equation (1) as [13].
0( ) ( ) cNF dB MDS dBm KT B= − (1)
Where,
MDS is the Minimum Detectable Signal (-102dBm) for
WCDMA network [13].
cB is the channel bandwidth for the WCDMA given as
5MHz [8]
k is the Boltzmann’s constant 23
(1.38 10 / )x J K−
0T is the ambient temperature in Kelvin 0( 290 )T k=
3.2. Computation Model for Unco-located Network
The Noise Floor (NFloor) level is stated in equation (2) as
[14].
0
10
10
s
floor
KT B NF
N mw
+
= (2)
where sB is the signal bandwidth of WCDMA is 3.84MHz
[8].
The minimum demodulation C/I ratio was obtained using
equation (3) [14].

0u floor
m
C
S N
I
 
= − 
 
(3)
Where, 0uS is the average received signal strength.
3.3. Computation Model for Unco-located Network
The difference in the received signal level for co-located
and unco-located networks gives the degraded received
signal power denoted by eta symbol ( )dBη . If the received
signal strength is degraded by η, then the interference plus
noise power ( )FTN is given by equation (4) [14].
0
10 10
10 10
s
FT floor
KT B NF
N N mw
η
η
+
= += (4)
The interfering power at the receiver input, represented by
a gamma symbol ( )γ in dBm is computed using equation (5)
[14].
1010log 10 10
10 10
s sKTB NF KTB NF
dBm
η
γ
+ + + 
− 
 
(5)
The minimum demodulation carrier-to-interference ratio
(dB) is given by equation (6) [14].
0 ( )c floor
m
C
S N
I
η
 
= − + 
 
(6)
Where 0cS is the average received signal strength for
co-located network.
4. Result and Discussion
Tables 2 and 3 showed the detailed summary of the
average measured data and computed results and Table 4
showed the average ranges of the generated values.
From Table 4, the received signal strength degradation
was considered in the range of 0.01 to 3.07 dB, using 0.09 as
the increment. The first and the second column showed the
range of degradation in the received signal strength and the
corresponding rise in total noise level after the system was
interfered. The third column was obtained using equation (5),
while the fourth column shows the decrease in interfering
level compared to the original noise level of the WCDMA.
The original noise level was obtained as -103dBm using
equation (2). The fifth and sixth columns were obtained
using equations (1) and (6) respectively. On the other hand,
column four, row one and row two showed that the noise
floor level of the system was 26.37dB and 16.32dB higher
than the interfering power level. This explained that the noise
floor levels are within an acceptable range. If the interfering
noise level is equivalent to the original noise level as shown
in row thirty-six, column three and column four, where the
interfering noise level was -103.02dB and the original noise
level was -103dB, the entire desired received signal at that
point will be completely corrupted. Hence, the received
signal strength at that instance was degraded by 3dB, given
rise to 88.3% degradation of the carrier to interference ratio.
Therefore, it is always important to ensure that the noise
floor level of the original signal is 3dB above the interference
noise level to maintain victim’s percentage ratio [8]. The
condition of such illustrated scenario could be improved by
adding 3dB to the original noise floor level. Columns six and
eight showed the minimum demodulation and percentage
degradation of carrier to interference ratio when the received
signal strength degraded by a value with the corresponding
noise rise of the same value. The C/I ratio degradation in
column seven was obtained by the difference in C/I ratio for
unco-located and co-located networks.
The Three Generation Partnership Project (3GPP)
specified a tolerable level of interference from the offending
transmitter to the victim receiver as -110 dBm/3.84 MHz
[15]. A spurious signal would be 7dB below the original
noise floor value and its presence would cause a received
signal strength degradation of 0.8 dB. Referring to the results
obtained in table 4, the interfering power level of the CDMA
2000 transmitter to the WCDMA receiver obtained as
-108.80dBm/3.84MHz was beyond the specified tolerable
level by the 3GPP. The stated condition necessitated the
development of the mitigation system using a BBPF. Figure
1, illustrated the detailed steps to obtained the desired filter
magnitude.
Table 2. Summary of the Average Measured Data
1 Average received signal power for the unco-located network (WCDMA) -109.69dBm
2 Average received signal power for the co-located network (WCDMA) -110.70dBm
3 Average transmitted power (CDMA-2000) 38.6dBm
4 Received signal strength degradation (η ) 1.01dBm
Table 3. Summary of the Evaluated Results
Noise floor for
the unco-located
site (dB)
Noise floor
for the
co-located
site (dB)
Interfering
power
level
(dBm)
Minimum
demodulation
C/I for the
unco-located
network
Minimum
demodulation C/I
for the co-located
network
C/I
degradation
% C/I
degradation
-103 -101.99 -108.80 -6.69 -8.71 2.02 30

Table 4. Average Ranges of the Generated Values
Received signal
strength
degradation
(dB)
Rise in total
noise level after
the system is
interfered (dBm)
Interfering
power level
dBm
Decrease in
interfering level
compare to the
original noise level
(dB)
Noise
figure
(NF) dB
Minimum
Demodulation
C/I ratio
C/I ratio
degradation
% C/I ratio
degradation
0.01 0.01 -129.37 26.37 5 -6.71 0.02 0.3%
0.10 0.10 -119.32 16.32 5 -6.89 0.20 3%
0.19 0.19 -116.39 13.49 5 -7.07 0.38 6%
0.28 0.28 -114.76 11.76 5 -7.25 0.56 8.4%
0.37 0.37 -113.50 10.50 5 -7.43 0.74 11%
0.46 0.46 -112.52 9.52 5 -7.61 0.92 14%
0.55 0.55 -111.70 8.70 5 -7.79 1.1 16.4%
0.64 0.64 -110.99 7.99 5 -7.97 1.28 19%
0.73 0.73 -110.40 7.37 5 -8.15 1.46 22%
0.82 0.82 -109.82 6.82 5 -8.33 1.64 25%
0.91 0.91 -109.32 6.32 5 -8.51 1.82 27%
1.00 1.00 -108.87 5.87 5 -8.69 2.0 30%
1.01 1.01 -108.80 5.80 5 -8.71 2.02 30%
1.09 1.09 -108.45 5.45 5 -8.78 2.09 31%
1.18 1.18 -108.06 5.06 5 -8.96 2.27 34%
1.27 1.27 -107.69 4.69 5 -9.14 2.45 37%
1.36 1.36 -107.34 4.34 5 -9.32 2.63 39%
1.45 1.45 -107.02 4.02 5 -9.5 2.81 42%
1.54 1.54 -106.70 3.71 5 -9.68 2.99 45%
1.63 1.63 -106.40 3.42 5 -9.86 3.17 47%
1.72 1.72 -106.13 3.13 5 -10.04 3.35 50%
1.81 1.81 -105.86 2.86 5 -10.22 3.53 53%
1.90 1.90 -105.61 2.61 5 -10.4 3.71 56%
1.99 1.99 -105.36 2.36 5 -10.58 3.89 58%
2.08 2.08 -105.12 2.12 5 -10.76 4.07 61%
2.17 2.17 -104.88 1.88 5 -10.94 4.25 64%
2.26 2.26 -104.66 1.66 5 -11.12 4.43 66%
2.35 2.35 -104.44 1.44 5 -11.3 4.61 69%
2.44 2.44 -104.23 1.23 5 -11.48 4.79 72%
2.53 2.53 -104.02 1.02 5 -11.66 4.97 74%
2.62 2.62 -103.82 0.82 5 -11.84 5.15 77%
2.71 2.71 -103.62 0.62 5 -12.02 5.33 80%
2.80 2.80 -103.43 0.43 5 -12.2 5.51 82%
2.89 2.89 -103.24 0.24 5 -12.38 5.69 85%
2.98 2.98 -103.10 0.10 5 -12.56 5.87 88%
3.00 3.00 -103.02 0.02 5 -12.60 5.91 88.3%
3.07 3.07 -102.88 -0.12 5 -12.74 6.05 90%

4.1. BBPF Design Procedure
The limits of spurious emission level by the Three
Generation Partnership Project Two (3GPP2) for CDMA far
offset from carrier is given as -13dBm/1MHz
(1GHz<f<5GHz) [16]. In order to guarantee that the affected
receiver’s performance will not degrade, the isolation
between the interfering transmitter and affected receiver
should be:
13 /1 ( 108.80 / 3.84 ) 101.8 102dBm MHz MHz dB− − − = ≈ (7)
The total isolation required to maintain optimum received
signal performance in the co-located scenario is 102dB. The
standard antenna-to-antenna isolation specification (dB) by
the NCC for personal communication system (PCS), digital
communication systems (DCS) and universal mobile
communication system (UMTS) in a co-located site is 50dB
[8].
Therefore a 52dB rejection at 5MHz guard band was
obtained as the required specifications for the BBPF offset
from the low side edge of the pass band. A guard band of
5MHz pass band was considered to offer a faster roll-off
space for the BBPF. Figure 2 illustrated the guard band
Figure 1. Steps to Obtain the Desired Filter Magnitude
Analyze the results
Compute the desired filter magnitude
Yes
is
dBm110−>γ ?
No
Yes
Start
Obtain the average reference received signal power for
unco-located WCDMA network
Obtain the average received signal power for co-located
WCDMA network
Obtain the average effective radiated power of CDMA
2000 network
Compute the difference in the received signal strength
degradation ( )η for the WCDMA network
Is
dB8.0>η ?
No
Compute the interfering signal power ( )γ for the co-located
CDMA 2000 Network
End

specification.
4.2. BBPF Design Specifications
The BBPF was primarily considered among other Infinite
Impulse Response (IIR) filters because of its attributes to the
least amount of phase distortion. Other features include the
transfer function of the filter offers maximally-flat response
at the pass band and stop band, signifying that its frequency
response decreases monotonically, exhibiting no ripples at
the pass band and stop band frequencies. This unique
characteristic performance shows that the phase linearity of
Butterworth filter is better than other IIR filters. Equation 8
[17], was used to convert the frequency(Hz) to normalized
frequency ( )ω .
2
s
f
f
π
ω = (8)
Where f is the absolute frequency in Hertz or
cycles/second, ,sf the sampling frequency in
samples/second and ω is the normalized frequency in π
radian/sample. Figure 3 illustrated the flowchart
implementation of the BBPF and Tables 5 and 6 showed the
frequency and magnitude specifications for the BBPF. The
graphs of magnitude response, phase response, group delay
performance, impulse response and pole/zero plots are
illustrated in Figures 4-9.
Table 5. Frequency and Normalized Frequency Specifications for the
BBPF
Filter parameters Magnitude specifications
Astop1 52dB
Apass 0.1dB
Astop2 52dB
Table 6. Magnitude Specifications for the BBPF
Filter
parameters
Frequency
specifications (KHz)
Normalized frequency
( )ω (π radian/samples)
Fstop1 1955000 0.4912= 1Stopω
Fpass1 1960000 0.4924= 1Passω
Fpass2 1990000 0.5000= 2Passω
Fstop2 1995000 0.5012= 2Stopω
Sampling frequency
7960000sf =
where;
Fpass1: Frequency at the edge of the start of the pass band.
Specified in normalized frequency units.
Fpass2 : Frequency at the edge of the end of the pass band.
Specified in normalized frequency units.
Fstop1 : Frequency at the edge of the start of the first stop
band, specified in normalized frequency units.
Fstop2 : Frequency at the edge of the start of the second stop
band, specified in normalized frequency.
Astop1: Attenuation in the first stop band in dB.
APass: Amount of ripple allowed in the pass band, known
as the single pass band gain parameter.
Astop2: Attenuation in the second stop band in dB.
Figure 2. The Guard Band specification
1920 1955 1960 1990 (MHz)
Center-to-Center Frequency of
25.2MHz
Uplink
WCDMA
Carrier
Downlink
CDMA2000
Carrier
Guard Band

Figure 4. The Magnitude Response Figure 5. The Phase Response
Figure 3. Flowchart Implementation of the BBPF
Specify the Filter parameters
Initialize the Magnitude Specifications
Compute the Normalized Frequency
Specifications of the filter
Realize the digital filter structure
Implement the designed digital filter
Start
Input the filter specifications in FDA
Tool
Is
the designed
digital filter stable?
No
Yes
Specify the options; matched exactly at pass
band
End
Analyze the digital filter response

Figure 6. Group delay response
Figure 7. The Impulse Response
Figure 8. The Pole and Zero Plot
4.3. Performance Evaluation Decisive Factors for the
BBPF Technique
The system performance of the BBPF technique was
evaluated using Noise Cancellation Performance (NCP)
criterion. This is important to assess the performance of the
designed system. The NCP is a measure of the cancellation
levels by which the noise signal power level in a certain
bandwidth is reduced [18]. It is mathematically defined as
the power ratio of the residual error signal to the primary
signal at the point of cancellation expressed in dB as shown
in equation (9) [18].
Pr
10log( )err
i
P
NCP
P
= (9)
where errP is the error signal in terms of average power
level and priP is the primary signals in terms of average
power levels.
Equations 10, 11, and 12 are used to plot the graph of
Amplitude Imbalance versus Noise Cancellation
Performance level, the graph of phase error against different
levels of Noise Cancellation Performance and the graph of
delay mismatch against Noise Cancellation Performance
levels respectively, as shown in Figures 9, 10 and 11. The
cancellation performances are used to describe various levels
achievable relative to the characteristic performances of the
amplitude imbalance, phase error and delay mismatch.
2
20 20( ) 10log 1 10 2.10
dB dB
dBNCP
γ γ
γ
  
= + − 
  
[18] (10)
[ ]( ) 10log 2(1 cos( ))err errNCP θ θ= − [18] (11)
( ) 10log[2(1 cos( )]NCP Bτ πτ= − [18] (12)
Figure 9. Amplitude imbalance Vs Noise Cancellation Performance(dB)
Figure 10. Phase Error(degrees) vs Noise Cancellation Performance(dB)

Figure 11. Time delay Mismatch (ns) vs Noise Cancellation Performance
(dB)
It is observed that to achieve a 52dB cancellation in
Figures 9, 10 and 11, the amplitude imbalance was below
0.03dB, the phase error was less than 0.140
. and the delay
mismatch did not exceed 0.07ns. Therefore, the minimum
requirements necessary to obtain a 52dB noise cancellation
performance are; γ <0.03dB, errθ < 0.140
and τ < 0.07ns.
The values obtained showed that the magnitude specification
obtained for the BBPF design could substantially attenuate
the transmitter noise components present in the WCDMA
receiver with minimal leakages considering the non-ideal
characteristic of a fixed filter.
5. Conclusions
The paper was designed at providing adequate solution to
mitigate the transmitter noise effect involving downlink
frequency of CDMA-2000 in the frequency range
(1960-1990MHz) and uplink WCDMA in the frequency
range (1920-1980MHz) in a co-located network. Empirical
analyses were conducted in two different scenarios to
evaluate the degree of interference power effects on the
victim receiver. The effects of the interfering noise power on
the received signal strength performance and its degradation
effects on the Carrier to Interference ratio were clearly
characterized using empirical analysis. The interfering
power was evaluated as -108.80dBm, which gave rise to
1.01dBm received signal strength degradation and 1.01dBm
rise in total system noise floor, about 30% degradation in C/I
ratio. A 52dB rejection band pass filter at 5MHz guard band
offset from the low side edge of the pass band was obtained.
The application of BBPF was used to attenuate the
significant effects of the transmitter noise. Conversely, an
NCP criterion was introduced to evaluate the various
performance characteristics at 52dB. This gave rise to
amplitude imbalance of less than 0.03dB, phase error below
0.140
and time delay mismatch below 0.07ns respectively.
The three values obtained in the research findings showed
that the magnitude specification of the 52dB rejection
obtained for the BBPF design can to a larger extent attenuate
the sideband noise components present in the WCDMA
receiver front end.
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