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Nie, dziękuję Przekieruj mnie tamwhat is a rakel receiver?
– Two different things are referred to by the expression “rakel receiver.”
Key points
• RAKEL = Swedish mission-critical network; equipment is tightly regulated, 380–400 MHz, encrypted.
• Rake = signal-processing technique for CDMA, W-CDMA, UWB, some 4 G/5 G; improves performance in multipath channels.
• Your intended meaning depends on context (public-safety radios vs. digital-communication theory).
1 . RAKEL receivers (public-safety TETRA terminals)
• Network basis: ETSI TETRA Release 1; carrier: 25 kHz; modulation: π⁄4-DQPSK; four TDMA timeslots ⇒ 28.8 kb s⁻¹ gross.
• Frequency allocation in Sweden: downlink 390–395 MHz, uplink 380–385 MHz.
• Typical hardware classes
– Hand portable (e.g. Motorola MTP-3000, Sepura SC-20)
– Vehicle/mobile (e.g. Airbus THR9, Sepura SRG3900)
– Fixed dispatcher or gateway/repeater (e.g. Airbus TB3-R, BHE BRTM-47 indoor repeater).
• Core functions
– TEA1/TEA2/TEA3 encryption, mutual authentication, Air Interface Encryption (AIE) and optional end-to-end.
– Group, individual, emergency and broadcast calls; status/SDS data; GPS/BeiDou/Galileo positioning.
– Fallback: Direct Mode Operation (DMO) with or without gateway/ repeater support.
• Regulatory aspects: Network operated by MSB (Swedish Civil Contingencies Agency). Only accredited agencies and suppliers can purchase or activate terminals; keys are managed by MSB’s Key Management Facility.
2 . Rake receivers (multipath-combining architecture)
• Multipath problem: Different reflections arrive with delays τᵢ and attenuations αᵢ, causing fading and inter-symbol interference (ISI).
• Rake principle:
a) Channel estimation finds significant paths (Peaks in matched filter).
b) Each “finger” despreads the chip-sequence with delay τᵢ.
c) Per-finger outputs are phase-aligned and weighted (usually Maximal-Ratio Combining):
\[ y = \sum{i=1}^{N\text{fingers}} w_i\,x_i \]
d) Decision device operates on the combined signal with improved SNR (diversity gain ≈ Σ|αᵢ|²).
• Finger count: 3–6 in early IS-95 handsets, 12 or more in W-CDMA Node-B/UE, dynamic finger reassignment in 5 G NR (when DSSS/SC-FDMA reference signals allow).
• Applications: IS-95, cdma2000 1xEV-DO, UMTS/W-CDMA (HS-DSCH rake in base stations), UWB impulse radios, some GNSS receivers (Delay-Lock Loops often viewed as 2-finger rakes).
• Implementation issues: search window length vs. power, finger scheduler ASIC/FPGA complexity, need for accurate timing (Δτ ≤ one chip period).
RAKEL (Sweden)
• Coverage > 99 % of population, > 95 % of landmass; > 80 000 active subscribers (MSB 2023 report).
• Migration path “Rakel G2”: MSB is tendering a 4G/5G mission-critical broadband service (MCX, 3GPP Rel-17). RAKEL TETRA voice will coexist until at least 2030.
• New terminals support TEDS (TETRA Enhanced Data Service, 150 kb s⁻¹ per carrier) and dual-mode LTE + TETRA.
Rake receiver technique
• Still embedded in 4G/5G chipsets for DSSS-based positioning, NB-IoT PRS combining, and in mm-wave massive-MIMO channel estimation (software “virtual rake”).
• Research focuses on low-power all-digital rake for IoT UWB (IEEE 802.15.4z HRP) and iterative turbo rake/equaliser combinations for 5G/New-Radio sidelink.
Analogy for rake: Each finger is like a tine of a garden rake collecting leaves (signal energy) that are scattered across the lawn (delay axis). When the tines are aligned and pushed together you get one pile (combined signal) instead of many small pieces.
Example calculation: In a W-CDMA environment with three dominant paths (–3 dB, –5 dB, –8 dB relative), combining them by MRC gives ≈ 3.3 dB SNR improvement over the strongest path alone, often the difference between FER < 1 % and link failure.
RAKEL terminals
• Cryptography export/import is controlled; breaking of TEA-keys or unauthorised cloning is illegal.
• User privacy: location services are visible to command centres but must comply with GDPR; logs retained by MSB.
• Spectrum is exclusive; any unlicensed transmitter in 380–400 MHz risks prosecution.
Rake technology
• Covered by historical Qualcomm/Philips patents; core claims have largely expired, but particular low-power implementations may be patented.
• No specific ethical issues; standard RF safety regulations apply.
RAKEL
1 . Procurement: Only buy from MSB-certified vendors; ensure firmware matches MSB key-loader version.
2 . Programming: Use authorised CPS; request ISSI/TETRA numbers from network operator.
3 . Coverage gaps: deploy channel-selective BHE BRTM-47 or Airbus TB3 Outdoor repeater; observe output EIRP limits (< 10 W ERP in band).
Rake receiver design
1 . Determine expected delay spread σ_τ; set search window W ≥ 5σ_τ.
2 . Design correlator bank: oversampling ≥ 2× chip-rate to ease fractional-chip delays.
3 . Implement adaptive combining (MRC > EGC > SC).
4 . Validate with channel emulator (e.g. Spirent VR5) using COST-207 TU, HT, RA profiles.
• RAKEL information is country-specific; other nations use TETRA under names such as Airwave (UK), SIRESP (PT).
• Rake receivers are less effective when delay spread > symbol duration (e.g. OFDM wide sub-carriers) – then a cyclic prefix plus frequency-domain equalisation is preferred.
RAKEL
• Transition to MCX over 5G and integration with broadband IoT sensors for blue-light services.
• Interoperability frameworks with Norway’s Nødnett and Finland’s Virve 2.
Rake
• Machine-learning-based path-selection to reduce finger count.
• Hybrid rake–MIMO equalizers for mm-wave vehicular communications.
Recommended resources
• MSB, “Rakel och framtidens radiokommunikation” (white paper, 2023).
• ETSI EN 300 392-2 V3.3.1, “TETRA Voice plus Data”.
• Qualcomm, “The Rake Receiver in CDMA IS-95,” Tech Note 1999.
• T. Ojanperä & R. Prasad, “WCDMA: Towards IP Mobility and Mobile Internet,” Artech House.
“RAKEL receiver” can mean either
• a mission-critical TETRA radio used on Sweden’s secure RAKEL network, or
• a “rake” receiver, an architecture that combats multipath by aligning and combining several delayed replicas of a spread-spectrum signal.
Knowing your context (public-safety radio procurement vs. wireless-communication theory) will determine which definition—and technical details—apply.
