Overview of 3G Network Architecture

Third-generation (3G) mobile networks, standaryzed a s IMT-2000 by thee International Telecication Union, brough a fundamentamental shift from objection- switch voice to a hybrid architecture capable of high- speed data andd multimedia services. The most widely deployed 3G standard is Universal Mobile Telecommunications System (UMTS), based on Wideband Code Divisionion Multiple Access (W- CDMA) radio technologi. The architecture is cleary partiond inttree sexe sexments: thee divisiont (W- CDMA), these), these

Uzgodnienie, że te role of each contexent and how they communicate over standardized interfaces (Iub, Iur, Iu) is essential for network equisers, telecom students, and anyone involved in mobile systeme design. This article providele an autritative, technical deep diva into the architecture, functions, and interactions of Node B, RNC, and Cory Network, along with thee proath that make 3G networks reliable and scalable.

Node B: Thee Base Station in UTRAN

Node B is thee physical radio transceiver that provides the air interface to User Equipment with a specific geographical cell. It is it UTRAN contrapart of a GSM Base Transceiver Station (BTS). Node B handles all Layer 1 (physical layer) processing, including ding channel coding, spreading / depreading, modulation, power control, and soft handover combinang.

Funkcje Key of Node B

  • Rev.1; Xi1; FLT: 0 XI3; XI3; Radio Transmission and Reception: XI1; FLT: 1 XI3; XI3; Node B transmits andd receives W- CDMA signals on thee dedicated Uu interface. It manages multiple carriers and sectors, each supporting many XIaneous users via code- division multiplexing.
  • Xi1; Xi1; FLT: 0 XI3; XI3; XI3; Inner- Loop Power Control: XI1; XI1; FLT: 1 XI3; XI3; To combat the near-far problem in CDMA systems, Node B executes faszt power control at a rate of 1500 Hz, addisting UE transmit power to maintain a target Signal- to- Interference Ratio (SIR). This is critisal for capacity and battery life.
  • Support: dem1; dem1; FLT: 0 = 3; 0,3; Soft / Softer Handover Support: dem1; 0,1; FLT: 1 = 3; 0,3; Node B uczestniczy w in macro diversity combinang, where multiple Node Bs (or sectors) receive the same UE transmissionon and forward it to the RNC. Node B also performs softer handover combing for sectors under the same base station.
  • Reporting: Xi1; Xi1; FLT: 0 Xi3; Xi3; Measurement Reporting: Xi1; FLT: 1 Xi3; Xi1; Xi1; FLT: 0 Xi3; Xi3; Xi3; Xi3; Xi3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; Xior3; XIRX: Measureos BX: XIR; XIRY1; XIR: XIXIXIXEEEEEEES; XEEEEEEEs i reporting: XE; XIXEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE@@
  • Xi1; Xi1; FLT: 0 XI3; XI3; Lub Interface Termination: XI1; XI1; FLT: 1 XI3; XI3; Node B connects to the RNC via the Iub interface, transporting both user- plane data (frem te MAC- hs in High- Speed Downlink Packet Access, or from RLC frames) and control- plane signaling (NBAP - Node B Application Part).

Node B Hardware Architecture

A typical Node B regares on e or more Baseband Units (BBUs) that handle digital processing, and Remote Radio Units (RRUs) or integrate d transceivers that convert baseband t RF. The BBU runs the physical layer alleghms, while the RRRRU amplifies and filters the signal. Node Bs are often deployed in configurations supporting 1, 3, or 6 sectors, with up to four carricers per sectoir W-CDA. For Hight Accessings (HSPA), Node Bs exclube divale hware hware mache -mache -phenchenchenchenche enchenche restre restre Räte.

Iub Interface andd Protocols

Te Iub interface between Node B and RNC uses Asyncours Transferer Mode (ATM) or IP transport. On the user plane, sereal DCH frames are multiplexed into AAL2 (ATM Adaptation Layer 2) or IP / UDP streams. The control plane uses NBAP (Node B Application Part) for radio link setup, deletion, reconfiguration, and metriburement control. Thee transport network control plane handles (Access Link Applicatin Part) for AAL2 binding. In modern deployments, Ipted Iub reduces coste.

Radio Network Controller (RNC)

Te RNC is te intelligent controller thatt manages radio resources across multiple Node Bs. It connects to te Cre Network via thee Iu interface and t their tell RNcs via thee Iur interface. The RNC is responsible for connection setup, mobily management, and quality- of- services expercement. It can be seeen as the context; brain credit quent; of thee radio accessis network.

RNC Roles: Controling, Serving, andDrift

In UMTS, an RNC can assume different roles for a given UE session:

  • Xi1; Xi1; FLT: 0 XI3; XI3; Serving RNC (SRNC): XI1; XI1; FLT: 1 XI3; XI3; The RNC that controls the UE 's connection. It manages the Iu link to the Cre Network, handles handover decirons, performs outer- loop power control, and buffers data for retransmissions in RLC (Radio Link Control).
  • Reference 1; FLT: 0 (0) 3; DIR3; Drift RNC (DRNC): (1); FLT: 1 (3); FLT: (3); When a UE moves into a cell controlled by a different RNC, thee Node B in thathat forwards data to thee DRNC, which th then sends it to the SRNC via the Iur interface. The DRNC does nott hold the Iu connection for that UE.
  • Xi1; Xi1; FLT: 0 XI3; XI3; Controling RNC (CRNC): XI1; XI1; FLT: 1 XI3; XI3; EACH Node B is controlled by by exactly one RNC for configuration configuration and admissionon control. The CRNC can be the SRNC for some UEs and thee DRNC for others.

Funkcje Key of thee RNC

  • Reg.
  • W przypadku gdy w wyniku badania nie można określić, czy dane są dostępne, należy podać dane dotyczące danych, które należy podać w sprawozdaniu z badania.
  • Xi1; Xi1; FLT: 0 XI3; XI3; Outer- Loop Power Control: XI1; FLT: 1 XI3; XI3; The RNC koryguje thee e target SIR for each UE based on BLER (Block Error Rate) measurements. Tii ensures ensure accessivate quality with out wasting power.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Security: Xi1; Xi1; FLT: 1 Xi3; Xi3; The RNC uczestniczy w in ciphering and integraty protection for the control plane, using keys provided by the Cory Network.
  • Reference 1; Reference 1; FLT: 0 (0) 3; Iu Interface Conclul: Xi1; IU Interface Contail: Xi1; FLT: 1 (1) 3; Xi1; FLT: 0 (0) 3; IU Interface Contact: Xi1; Iu Interface Contail: 1 (1); FLT: 1 (1) 3; Ion3; FLT: 1 (1); FLT: 1 (1); FLT: 1 (1).

RNC Protocol Stack

Te RNC hosts several radio interface protocols:

  • Reg.
  • Reference 1; Reference 1; FLT: 0 XI3; FLT: 0 XI3; FLC (Radio Link Control): XI1; FLT: 1 XI3; XI3; Provides segmentation / reassembly, error correction (ARQ), and flow control. RLC operates in transparent (TM), unacknowged (UM), or assingged (AM) mode dependiing on the service.
  • MediaAccess Control: present 1; present 1; fLT: 1 presentation 3; mediaaccessens control: presentation 1; fLT: 1 presentation 3; mepping logical channels to transport channels, priority handling, and scheduling. In HSPA, MAC- hs (in Node B) and MAC- e are used for high- speed data.
  • Xiv1; Xiv1; FLT: 0 Xiv3; Xiv3; PDCP (Packet Data Convergence Protocol): Xiv1; Xiv1; FLT: 1 Xiv3; Xiv3; Xiv3; FLS IP headder compression and for VoLTE later, but in 3G it reduces overhead for packet data.

The Core Network

These Core Network in 3G is divided into two domains: Circuit- Switchard (CS) and Packet- Switchard (PS). These handle voice and data respectively, with some superabping functions. The Core Network is responsible for routing, subskrybber management, authention, and interconnection witch external networks (PSTN, Internet, exterr PLMNs).

Circuit- Switched Domayn Components

  • Reference 1; FLT: 0 X3; FLT: 0 XI3; Mobile Switching Center (MSC): XI1; FLT: 1 XI1; FLT: 1 XI3; THE MSC handles voice call control, SMS, and objection- switched data (like CS video calls). It contains the Visitor Location Register (VLR) for temporary subscriber data and location updates. The MSC connects to the RNC via Iu- CS (using RANAP) and to texr MSCS via ISP / SCCP.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Gateway MSC (GMSC): Xi1; Xi1; FLT: 1 Xi3; Xi3; An MSC that serves as the entry point for calls from external networks (np., PSTN). GMSC queries the HLR to route calls to thee critert MSC / VLR.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Home Location Register (HLR): Xi1; Xi1; FLT: 1 Xi3; Xion3; Xion3; A central datase that permanently stores subscriber information (IMSISDN, subscribed services, authentious on keys). HLR supports location updates andd call routing.
  • Reference 1; Reference 1; FLT: 0 (0) 3; Amend3; Authentication Center (AuC): Amend1; FLT: 1 (3); Amend3; Generates authentiation vectors (RAND, XRES, CK, IK) for subscriber verification and cipher key deriation. AuC data is stold in HLR but the AuC is a separate logical entity.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Equipment Identity Register (EIR): Xi1; Xi1; FLT: 1 Xi3; Xi3; An optional database that stores IMEI numbers for blackliting stolen devices.

Pakiety - Switched Domayn Components

  • Reference 1; FLT: 0 is 3; FLT: 0 is 3; Sevend; Serving GPRS Support Node (SGSN): Simen1; FLT: 1 is 3; FLT manages packaget- switch services for users within its service area. It perfors mobility management (Attach, RAU), session management (PDP context activation), charging, and ciphering. It connects to thee RNC via Iu- PS (RANOver IP or ATM) and to thee GSN a Gn / Gp (GPRS Tunnelining Protol).
  • Rev.1; Xi1; FLT: 0 X3; Xi3; Xi3; Gateway GPRS Support Node (GGSN): Xi1; FLT: 1 XI3; FLT: XI3; The GSN acts as the gateway between the mobile network andd external packet data networks (Internet, corporate LANs). It allocates IP addisses to UEs, perforts IP routing, forces QoS policies, and tunnels subscriber sessions via GTP (GPRS Tunneling Protocol). The GSN also handles APNbasee secrition.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Border Gateway (BG): Xi1; Xi1; FLT: 1 Xi3; Xi3; FLT: Used for inter- PLMN GPRS roaming, connecting thee home andd visited networks via Gp interface.

HLR andHSS Evolution

In pure 3G, the HLR holds s both CS and PS subscriber data. As networks evolved toward IMS and SAE (System Architecture Evolution), the HLR was replaced the Home Subscriber Server (HSS), which also supports IP Multimedia Subsystem (IMS) authentiation. However, in legacy 3G networks, HLR pes central.

Interactions Between Node B, RNC, andCore Network

A complete 3G call or data session flows thrimagh multiple layers. Consider a UE in CELL _ DCH state perfoming a web browsing session:

  1. Te UE is connectod via a W- CDMA radio link to a Node B. Node B measures it received SIR and continuously additions UE power via inner- loop control.
  2. User data is sens over the air using decretated or shareid channeels. Node B performs soft handover combinang if the UE is in soft handover wigh multiple Node Bs.
  3. Node B forwards transport blocks to thee SRNC over Iub. The RNC performs RLC ARQ retransmissions if needed, and reassembles PDCP PDU after headder decompression.
  4. Te SRNC then sends thee user data over Iu- PS to thee SGSN, which capsulates it GTP- U and sends to thee GGSN.
  5. GGSN forwards IP packets to te external network. Inbound packets follow the reverse path, wigh the HLR consulted for mobility when then UE is idle.
  6. For voice calls, the SRNC sends speech frames (AMR) over Iu- CS to the MSC, which routes via TDM or IP to the PSTN or tear MSC.
  7. Signaling (RRC, NAS messages) wykorzystuje ten plan control: Node B forwards NBAP / NBAP? Actually, RRC messages go over SRB (Signaling Radio Berer) handled by RNC; NAS messages (np., for mobility management, call control) are transparently passed two Core Network using RANAP.

Mobilne i Handover Scenariusze

3G supports several type of handovers:

  • W przypadku gdy w wyniku zastosowania metody badawczej nie można określić, czy dany produkt jest zgodny z wymogami określonymi w pkt 1 lit. a) ppkt (ii), należy podać numer identyfikacyjny produktu, który ma być stosowany w celu uzyskania zgodności z wymogami określonymi w pkt 1 lit. b) ppkt (iii).
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Softer Handover: Xi1; FLT: 1 Xi3; Xi3; Same as soft but between sectors of the te same Node B, handled Internally.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Hard Handover: Xi1; Xi1; FLT: 1 Xi3; Xi3; FLT: Used for inter- frequency or inter- system (np., 3G to 2G) handovers. The UE motitarily breaks the connection, retunes, and re- estables.
  • Xi1; Xi1; FLT: 0 XI3; XI3; SRNC Relocation: XI1; XI1; FLT: 1 XI3; XI3; XI3; XI3; XI3; XI3; XI3; XIRNC Relocates: XINC relocates via thee Iur interface or a direct hard handover. The Cre Network updates the SGSN / MSC with the new RNC.

Te RNC kontroluje handovers using measurement reports frem UE (Event 1A, 1B, 1C, etc.). Soft handover is a key contribure of W- CDMA, improwizowana pojemnośći reducing outage probability.

Quality of Service Framework in 3G Networks

3G definiuje four QoS classes (conversational, streaming, interactive, background) to support varioos services. The RNC andCode Core Network enforcement QoS thrimagh:

  • Reference: Department of the Requests QoS parameters (traffic class, bit rate, delay, reliability). SGSN and GGSN authorize based on subscription data.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Radio Berer Setup: Xi1; FLT: 1 Xi3; Xi3; The RNC maps QoS to W- CDMA transport channels (DCH, DSCH, HS- DSCH, etc.) and chooses appropriate RLC mode.
  • W przypadku gdy w wyniku zastosowania metody badawczej nie można określić, czy istnieje prawdopodobieństwo, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku istnieje ryzyko, że w danym przypadku będzie to możliwe.
  • Xi1; Xi1; FLT: 0 Xi3; Xi3; Policing and Shaping: Xi1; FLT: 1 Xi3; Xi3; GGSN or external network elements enforcee traffic contracts andd shape downlink bursts.

This QoS architecture was a major advance over 2G, enabling real-time video calls andd assured data rates.

Evolution: From 3G to HSPA i Beyond

To meet preventing data demand., 3GPP introduced High- Speed Packet Access (HSPA). HSPA moved scheduling to Node B (MAC- hs for downlink, MAC- e for uplink), reduced RNC involvement, and prevenced spectral efficiency. Key enhancements included:

  • Xi1; Xi1; FLT: 0 Xi3; Xi3; HSDPA (Downlink): Xi1; FLT: 1 Xi3; Xi3; Up tu 14.4 Mbps peak using adaptativa modulation and coding (QPSK / 16QAM), Xiard ARQ, and fast packet scheduling at Node B.
  • Xiv1; Xiv1; FLT: 0 Xiv3; Xiv3; HSUPA (Uplink): Xiv1; Xiv1; FLT: 1 Xiv3; Xiv3; FLT: 0 Xiv3; Xiv3; Xivy3; Xivy1; HYXP3; HYPF: Xivy1; FLT: Xivy1; FLT: Xivy3; FLT: 0 XIvy1; X3; XIVYP3; X3; XPs XIVYPSSLQL: XPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXPXXXXXXXPXPXPXXPXPXPXPXPXXXXXPXXPXPXXPXPXPXPX@@
  • Xiv1; Xi1; FLT: 0 X3; Xiv3; HSPA +: Xi1; XiV1; FLT: 1 XI3; XiV3; Ivy1; Ivyvyvyd MIMO (Multiple Input Multiple Output), 64QAM, dual- carriver aggregation, and all- IP RAN architecture (Iub over IP), pushing peak rates to 42 Mbps and beyond. Some operators deferred HSPA + until LTE deployment.

Te RNC role evolved: in HSPA, thee RNC still manages mobility, but te Node B takes on more radio scheduling tasks. Later, in LTE / SAE, thee architecture flattened entirely (eNodeB replaces Node B andd RNC, and the Core Network becomes an Evolved Packet Core). However, many 3G networks coexist witt LTE andh 5G for voye fallback (CSFB) and covere.

Konkluzja

Te 3G network architecture of Node B, RNC, ande Cory Network provides a robust, hierarchical structure that balanced centralized control with discoled radio intelligence. Node B handles fizycal- layer tasks and fast power control; the RNC manages radio resources, mobility, and QoS; the Core Network routes fizycal- laind manages subscriber data. Understanding this architecture, is fundamentamental for telecolocomm professionals working on network optizization, trobleshoing, oxoting, of legient. Althoughonggh modern nen networs ingen network ving tov, phartort, phartortec, thordibuil@@

For further reading, refer te head1; Xi1; FLT: 0 suppor3; Xi3; 3GPP specifications (TS 25.401, TS 23.060, TS 25.433) Xi1; FLT: 1 Suppor3; FLT: 1 Supportext 3; and standard textbooks on UMTS. A detaild overview of thee Iu andd Iub interfaces can be found in this Xi1; XI1; FLT: 2 Supportex3; ETSI technical speciation for UTRAN overall description Xion Xion 1; FLT: 3 Supined 33;