PROPOSALS TO IMPROVE THE TECHNICAL CHARACTERISTICS OF BROADBAND RADIO
COMMUNICATIONS UNDER THE CONDITIONS OF HARD RESTRICTIONS ON THE PROVIDED FREQUENCY
RESOURCE
Savelyeva M.V. Candidate of Technical Sciences, Researcher of the 12th SIC, VA of the Peter the Great
RVSN
Nekrasov A., teacher, VA of the Peter the Great RVSN, sanya.nekrasov.1992@mail.ru
Abstract: The article evaluates the capacity of promising radio communication systems with coherent
frequency-code division of channels in a limited dedicated frequency band and quadrature amplitudeinverse modulation of complex signals.
Prospects for the development of wireless communication systems. The intensive development of
cellular, wireless, satellite and professional stationary and mobile radio communication systems has led
to the active use of the frequency resource. The limited frequency resource and the increased need for it
have led to the need to find ways to rationally use it.
The main feature of promising radio communication systems is the need to meet high requirements for
mechanical protection and information transfer rate in a limited dedicated band of the radio frequency
spectrum. These requirements are in sharp contradiction with the limitedness of the allocated frequency
resource.
The authors propose fundamentally new solutions on the principles of building radio communication
systems with the specified restrictions.
1. Application of orthogonal code multiplexing of channels based on full code rings [1].
2. Application of multi-basic energy efficient types of signal modulation, for example, such as quadrature
amplitude-inverse signal modulation [2].
3. Orthogonal channel multiplexing at coherent frequencies [3].
Let there be a coherent frequency grid with a fixed spacing of adjacent frequencies by the value
∆𝐹 =
1 𝑇
= ,
𝑇 𝑁
where T is the period of binary pseudo-random sequences from an ensemble of full code rings used for
orthogonal code division of information channels at each coherent frequency;
N is the length of the code sequence;
2F is the bandwidth allocated to the radio communication system.
A mathematical model of signal packing using spectral-efficient modulation. For any pair of a coherent
frequency grid, the phase difference of an even trigonometric function must satisfy the equation:
∆𝜑 = 𝜑𝑖 − 𝜑𝑗 =
𝜋
(2𝑘 + 1); 𝑖 − 𝑗 = 𝑘; 𝑘 = 0, 1, 2, …,
2
where cos(Δ𝜑) = 0,
for the uneven function
∆𝜑 = 𝜑𝑖′ − 𝜑𝑗 = 𝜑𝑖 − 𝜑𝑗′ = 𝜋𝑘;
where sin(Δ𝜑) = 0.
In this case, quadrature signals can be represented as follows:
𝑦𝑖 (𝑡) = 𝐴𝑖 cos(𝜔𝑖 𝑡 + 𝜑𝑖 ),
𝑥𝑖 (𝑡) = 𝐴𝑖 sin(𝜔𝑖 𝑡 + 𝜑𝑖 ),
𝑦𝑖′ (𝑡) = 𝐴𝑗 cos(𝜔𝑗 𝑡 + 𝜑𝑗 ),
𝑥𝑗′ (𝑡) = 𝐴𝑗 sin(𝜔𝑗 𝑡 + 𝜑𝑗 ),
where ω is the angular frequency, ω=2π/τ, τ=T/N, i. e. ω= 2πN/T;
τ is the character duration of the code sequence.
Let us show that quadrature radio communication channels at coherent frequencies are
orthogonal.
Then:
𝑇
𝑧(𝑡) = ∫ 𝐴𝑖 sin(𝜔𝑖 𝑡 + 𝜑𝑖 ) 𝐴𝑗 sin(𝜔𝑗 𝑡 + 𝜑𝑗′ ) 𝑑𝑡 =
0
=
𝑇
1
𝐴𝑖 𝐴𝑗 ∫ {cos[(𝜔𝑖 − 𝜔𝑗 )𝑡 + 𝜑𝑖 − 𝜑𝑗′ ] −
2
0
−𝐜𝐨𝐬[(𝝎𝒊 + 𝝎𝒋 )𝒕 + 𝝋𝒊 + 𝝋′𝒋 ]}𝑑𝑡 =
=
𝑇
1
𝐴𝑖 𝐴𝑗 ∫ {cos[(𝜔𝑖 − 𝜔𝑗 )𝑡 + 𝜑𝑖 − 𝜑𝑗′ ]} 𝑑𝑡 = 0,
2
0
as an integral of an integer number of periods.
What is meant here is that the sum frequency component (shown in bold) is outside the frequency
band passed by the low-pass filter.
Similarly,
𝑇
𝑧 ′ (𝑡) = ∫ 𝐴𝑖 cos(𝜔𝑖 𝑡 + 𝜑𝑖 ) 𝐴𝑗 cos(𝜔𝑗 𝑡 + 𝜑𝑗′ ) 𝑑𝑡 =
0
=
𝑇
1
𝐴𝑖 𝐴𝑗 ∫ {cos[(𝜔𝑖 − 𝜔𝑗 )𝑡 + 𝜑𝑖 − 𝜑𝑗′ ] +
2
0
+𝐜𝐨𝐬[(𝝎𝒊 + 𝝎𝒋 )𝒕 + 𝝋𝒊 + 𝝋′𝒋 ]}𝑑𝑡 =
𝑇
1
= 𝐴𝑖 𝐴𝑗 ∫ {cos[(𝜔𝑖 − 𝜔𝑗 )𝑡 + 𝜑𝑖 − 𝜑𝑗′ ]}𝑑𝑡 = 0,
2
0
as an integral of an integer number of periods.
At each m - th (from M) coherent frequency, its own set of N wideband signals with orthogonal
code division of channels is transmitted, formed by its own transmitting module. In each channel,
information is transmitted by means of quadrature multi-level amplitude-inverse modulation of code
sequences. This type of modulation can reduce power consumption by 6 dB.
On the receiving side, each transmitting module has its own receiving module, and the coherent
frequencies have different initial phases. This fact is fundamentally important, since on the receiving side
it is necessary to provide in-phase processing of the signals of each module separately, associated with
the corresponding coherent frequencies having different initial phases.
Estimation of the throughput of promising data transmission. Let us estimate the throughput of
the proposed information transfer method.
The specific throughput of a single-channel wide-band communication system with quadrature
channels and a code length of N chips (T is the sequence period) and with inverse binary modulation is
the following:
𝐶 = 2𝑅⁄(2𝐹),.
where F is the clock frequency of the formation of the sequence, equal to half the width of the
signal spectrum;
2R is the information transfer rate in each quadrature channel.
Bandwidth of N-channel communication system
𝐶 = 2𝑅𝑁⁄(2𝐹).
The throughput of an N-channel communication system at L coherent frequencies
𝐶 = 2𝑅𝑁𝐿⁄(2𝐹).
The use of multi-core modulation m quadrature amplitude-inverse signal modulation (m = 8) can
significantly increase the throughput of the communication system
𝐶 = 2𝑚𝑅𝑁𝐿⁄(2𝐹).
For example, for m = 8 and L = 5, the specific capacity of the communication system will be:
𝐶 = 2𝑚𝑅𝑁𝐿⁄(2𝐹) = 𝑚𝐿 = 40.
The proposed technical solution, aimed at increasing the throughput of broadband radio
communication systems, is unique in the sense that it allows, instead of losing, to obtain a significant gain
in throughput while maintaining the high noise immunity inherent in broadband radio communication
systems.