1796 IEEE COMMUNICATIONS LETTERS, VOL. 16, NO. 11, NOVEMBER 2012
DOD and DOA Estimation in
Bistatic Non-Uniform Multiple-Input Multiple-Output Radar Systems
Bobin Yao, Student Member, IEEE, Wenjie Wang, Member, IEEE,andQinyeYin
Abstract—This letter investigates the joint estimation of the
direction of departure (DOD) and direction of arrival (DOA)
for multi-input multi-output (MIMO) radar systems. A novel
estimation method based on non-uniform array configuration is
proposed and the practical identifiability of the corresponding
parameter is analyzed. The key idea is to use the Doppler
diversity to construct a virtual MIMO array. Through the
theoretical proof, we demonstrate that the proposed method can
provide much stronger parameter identifiability than the con-
ventional ones, and also can improve the parameter estimation
performance. Numerical simulations verify the effectiveness of
the proposed algorithm.
Index Terms—Multiple-input multiple-output radar, non-
unform array, parameter identifiability, angle estimation.
I. INTRODUCTION
J
OINT estimation of direction of departure (DOD) and
direction of arrival (DOA), as an important method for
exploiting the opportunistic space-division multiple access
(OSDMA) in wireless communication system [1] or moving
target localization in multiple-input multiple-output (MIMO)
radar system [2], [3], [ 4], [5], has been attracted lots of
attention. Two-dimension multiple signal classification (MU-
SIC) algorithm [3] and its reduced dimension version [4]
were exploited separately, both of which have almost the
same performance. The rotational invariance technique have
been studied in [5], however the performance is inferior
to the MUSIC based algorithms. Moreover, the parameter
identifiability also needs to be discussed elaborately, which
is a natural pre-requisite for a well-posed estimation problem.
The authors in [6] proved that the maximum number of targets
that can be uniquely identified by co-located uniform MIMO
radar (i.e., uniform linear arr a y is utilized on both transmit
and receive ends) is up to M times as that of the conventio nal
uniform phased radar, where M is the number of transmit
antennas. It also shows in [7] that the bistatic uniform MIMO
radar with single pulse in a coherent process interval provides
a identifiability upper bound 0.34M (N +1),whereN is the
number of receive antennas.
To further impr ove the parameter identifiability and the
estimation performance, we utilize a bistatic non-uniform
MIMO array in this letter. The non-uniform means that the
Manuscript received July 25, 2012. The associate editor coordinating the
review of this letter and approving it for publication was H. Wymeersch.
The authors are with the MOE Key Lab for Intelligent Networks and
Network Security, Xi’an Jiaotong University, Xi’an, 710049, Shaanxi, P. R.
China (e-mail: yaobobin@gmail.com).
This work was partially supported by the NSFC (No. 60971113, 61172093),
the Ph.D. Programs Foundation of Ministry of Education of China (No.
200806980020) and the Foundation for Innov a tive Research Groups of the
NSFC (No. 60921003).
Digital Object Identifier 10.1109/LCOMM.2012.091212.121605
antenna locations normalized by half carrier wavelength are
not a series of consecutive integers. The typical examples
are the minimum redundancy (MR) array [8], nested array
[9] and coprime array [10]. We herein develop a novel joint
DOD and DOA estimation algorithm, the kernel of which is
to use the Doppler diversity to construct a large virtual MIMO
array with more degree of freedom (DOF). The proposed
scheme is proved to be possessed of much stronger parameter
identifiability and much better estimation performance than the
conventional uniform MIMO arr ay. Meanwhile, it is also with
lower computational complexity and requires no parameter
pairing.
Notation: (·)
∗
, (·)
T
, (·)
H
, (·)
†
denote the complex conju-
gate, transpose, Hermitian transpose, pseudo-inverse, respec-
tively. Symbol “⊗” denotes Kronecker product and “” stands
for Khatri-Rao product (column-wise Kronecker product). I
M
is a M × M identity matrix and 0 symbolizes zero matrix.
A
(m)
is a submatrix o f A formed by its last m rows.
II. N
ON-UNIFORM MIMO RADAR FOR TARGET
LOCAL IZATION
A. Data Model
Consider a b istatic MIMO radar system with M -antenna
transmit array and N-antenna receive array, both o f which
are in non-uniform configuration. It is also assumed that there
are K targets, and the output baseband signal of the matched
filters at the receive array can be written as [4] [5] [7]
y(t)=[b(φ
1
) ⊗ a(θ
1
), ··· , b(φ
K
) ⊗ a(θ
K
)]h(t)+z(t) (1)
where the transmit steering vector a(θ
k
) and the receive
steering vector b(φ
k
),fork =1, 2, ··· ,K, are assumed to
be unchanged during a coherent processing interval (CPI),
and θ
k
,φ
k
are the DOD and DOA of the kth target, re-
spectively. The vector h(t)=[γ
1
(t), ··· ,γ
K
(t)]
T
relies
on the Doppler frequency f
dk
and the radar cross section
(RCS) coefficient β
k
, i.e., γ
k
(t)=β
k
e
j2πf
dk
(t−1)
.Note
that a(θ
k
)=[e
jπl
1
sin θ
k
, ··· ,e
jπl
M
sin θ
k
]
T
and b(φ
k
)=
[e
jπl
1
sin φ
k
, ··· ,e
jπl
N
sin φ
k
]
T
are mutilated Vandemonde vec-
tors, where l is the antenna location normalized by half carrier
wavelength. z(t) is the additive zero-mean Gaussian noise
with covariance σ
2
n
.
Defining A =[a(θ
1
), ··· , a(θ
K
)] ∈ C
M×K
, B =
[b(φ
1
), ··· , b(φ
K
)] ∈ C
N×K
, and after collecting Q consec-
utive pulses, (1) can be rewritten by the following compact
form
Y =(B A)H + Z (2)
where Y =[y(1), ··· , y(Q)], H =[h(1), ··· , h(Q)] and
Z =[z(1), ··· , z(Q)].
1089-7798/12$31.00
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2012 IEEE