Harman Becker Designs and Verifies OFDM Radio Receivers

Challenge

使用OFDM开发符合标准的数字无线电接收器

Solution

使用Mathworks工具进行基于模型的设计来建模，模拟，验证和评估数字接收器设计

Results

  • Design verified early in development
  • Communication between development teams improved
  • Baseband model development accelerated

"A low bit error rate provides an easy way for us to distinguish Harman Becker products from those of our competitors. Model-Based Design with MathWorks tools enabled us to evaluate this key metric in our designs months—if not years—earlier than was previously possible."

Axel Westenweller，Harman Becker汽车系统
Harman Becker radio and navigation device.

Engineers at Harman Becker Automotive Systems are developing the next generation of automotive audio and video systems using orthogonal frequency-division multiplexing (OFDM), a multicarrier modulation scheme for wideband digital communications. Their goal is to implement multiple digital broadcast standards like Digital Audio Broadcasting (DAB) and Digital Radio Mondiale (DRM) on a single device.

Harman Becker工程师使用Mathworks工具进行基于模型的设计来建模和模拟接收器基带算法，估计位错误率（BER）性能，验证初始设计以及使在不同领域工作的团队合作。以前，设计验证需要更加昂贵且耗时的方法，包括广泛的C编程和硬件原型 - 如果有的话，在设计周期后期发现了问题。

“位错误率是区分我们产品的接收器性能度量，” Harman Becker信号处理高级开发工程师Axel Westenweller解释说。下载188bet金宝搏“通过对Simulink进行建模，模拟和验证我们的设计，我们能够对系统的BER进行准确，快速的评估，从而使我金宝app们能够很早就做出关键的设计决策。”

Challenge

The engineers needed a golden reference that would enable them to estimate BER performance well before the design would be committed to hardware.

Westenweller指出：“我们需要工具在设计过程中尽快模拟BER性能，以便我们可以确定在硬件中必须纠正哪些错误，以及在基带算法中必须补偿哪些错误。”

Harman Becker also needed to verify the fixed-point performance of the system using a standardized library of C functions that numerically matched the fixed-point compiler intrinsic instructions optimized for the target DSP.

Solution

使用MATLAB®, Simulink®, and Communications Toolbox™作为其集成和验证环境，Harman Becker工程师对数字广播标准进行了建模，模拟，可视化和验证的基带实现。金宝appSimulink模拟使他们能够验证设计的每个阶段，并快速了解操作特征，包括信号星座和功率频谱密度。

团队将任务分为多个段，包括通道编码和解码，OFDM调制和解调，褪色的传播通道以及与硬件相关的RF损伤（例如热噪声和相位噪声）。他们使用simuli金宝appnk开发了数字基带层的浮点模型，其中包括通信工具箱中的Viterbi通道解码器。

The DAB standards require a differential quaternary phase shift keying (DQPSK) symbol mapping, including frequency interleaving. To meet this requirement, Harman Becker engineers created a customized DQPSK block in MATLAB, which they included in their Simulink model as a MATLAB S-function. The team captured real-world digitized intermediate frequency (IF) data produced by an RF front end. To verify the OFDM demodulation and channel decoding, they used this data as input for Simulink simulations, comparing the resulting data with the original, transmitted data.

With Simulink they simulated the influence of phase noise. Bit error rates were analyzed using BERTool in Communications Toolbox. Using the Simulink model as a golden reference, Harman Becker engineers verified the floating-point functionality of their design before replacing Simulink blocks in the model with fixed-point S-function equivalents written in C. The team could then verify the implementation executing on the TI C6000 DSP in bit-true fashion.

The team uses Rician and Rayleigh fading channels from Communications Toolbox to model real-world wireless communication phenomena, including multipath propagation and Doppler shifts.

RF和数字系统团队正在共同努力以参数化该模型，以匹配RF前端的现实性能。在目标硬件上正在开发设计的定点实现。

Results

  • Design verified early in development。金宝appSimulink使Harman Becker工程师能够在开发过程的早期彻底验证其设计，避免返工和昂贵的下游问题。Westenweller说：“在一个早期类似的项目上没有数学工具的工作，花了3到4个工程师年才能进行BER测试。”“使用Mathworks工具，我们将这段时间减少了至少75％。”

  • Communication between development teams improved。“这是非常重要的对我们的公司有一个executable specification that all engineering departments agree on," says Westenweller. "Our RF team and our digital systems development teams can use MATLAB and Simulink as a common language."

  • Baseband model development accelerated。"For us, a key advantage of using Simulink and Communications Toolbox is the ability to rapidly build a baseband model using the building blocks provided and add detail as needed," says Westenweller. "Without MathWorks tools, we would spend too much time and effort building these blocks in C instead of exploring and evaluating design options."

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