diff --git a/mixnet/connection.py b/mixnet/connection.py
index bf39cbc..8230e31 100644
--- a/mixnet/connection.py
+++ b/mixnet/connection.py
@@ -1,5 +1,6 @@
 import abc
-import asyncio
+
+from mixnet.framework.framework import Framework
 
 
 class SimplexConnection(abc.ABC):
@@ -13,8 +14,8 @@ class SimplexConnection(abc.ABC):
 
 
 class LocalSimplexConnection(SimplexConnection):
-    def __init__(self):
-        self.queue = asyncio.Queue()
+    def __init__(self, framework: Framework):
+        self.queue = framework.queue()
 
     async def send(self, data: bytes) -> None:
         await self.queue.put(data)
diff --git a/mixnet/framework/__init__.py b/mixnet/framework/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/mixnet/framework/asyncio.py b/mixnet/framework/asyncio.py
new file mode 100644
index 0000000..78ff3ea
--- /dev/null
+++ b/mixnet/framework/asyncio.py
@@ -0,0 +1,43 @@
+from __future__ import annotations
+
+import asyncio
+import time
+from typing import Any, Awaitable, Coroutine
+
+from mixnet.framework import framework
+
+
+class Framework(framework.Framework):
+    def __init__(self):
+        super().__init__()
+
+    def queue(self) -> framework.Queue:
+        return Queue()
+
+    async def sleep(self, seconds: float) -> None:
+        await asyncio.sleep(seconds)
+
+    def now(self) -> float:
+        return time.time()
+
+    def spawn(
+        self, coroutine: Coroutine[Any, Any, framework.RT]
+    ) -> Awaitable[framework.RT]:
+        return asyncio.create_task(coroutine)
+
+
+class Queue(framework.Queue):
+    _queue: asyncio.Queue[bytes]
+
+    def __init__(self):
+        super().__init__()
+        self._queue = asyncio.Queue()
+
+    async def put(self, data: bytes) -> None:
+        await self._queue.put(data)
+
+    async def get(self) -> bytes:
+        return await self._queue.get()
+
+    def empty(self) -> bool:
+        return self._queue.empty()
diff --git a/mixnet/framework/framework.py b/mixnet/framework/framework.py
new file mode 100644
index 0000000..5bbfaa1
--- /dev/null
+++ b/mixnet/framework/framework.py
@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+import abc
+from typing import Any, Awaitable, Coroutine, TypeVar
+
+RT = TypeVar("RT")
+
+
+class Framework(abc.ABC):
+    @abc.abstractmethod
+    def queue(self) -> Queue:
+        pass
+
+    @abc.abstractmethod
+    async def sleep(self, seconds: float) -> None:
+        pass
+
+    @abc.abstractmethod
+    def now(self) -> float:
+        pass
+
+    @abc.abstractmethod
+    def spawn(self, coroutine: Coroutine[Any, Any, RT]) -> Awaitable[RT]:
+        pass
+
+
+class Queue(abc.ABC):
+    @abc.abstractmethod
+    async def put(self, data: bytes) -> None:
+        pass
+
+    @abc.abstractmethod
+    async def get(self) -> bytes:
+        pass
+
+    @abc.abstractmethod
+    def empty(self) -> bool:
+        pass
diff --git a/mixnet/framework/usim.py b/mixnet/framework/usim.py
new file mode 100644
index 0000000..49e443d
--- /dev/null
+++ b/mixnet/framework/usim.py
@@ -0,0 +1,44 @@
+from typing import Any, Awaitable, Coroutine
+
+import usim
+
+from mixnet.framework import framework
+
+
+class Framework(framework.Framework):
+    _scope: usim.Scope
+
+    def __init__(self, scope: usim.Scope) -> None:
+        super().__init__()
+        self._scope = scope
+
+    def queue(self) -> framework.Queue:
+        return Queue()
+
+    async def sleep(self, seconds: float) -> None:
+        await (usim.time + seconds)
+
+    def now(self) -> float:
+        return usim.time.now
+
+    def spawn(
+        self, coroutine: Coroutine[Any, Any, framework.RT]
+    ) -> Awaitable[framework.RT]:
+        return self._scope.do(coroutine)
+
+
+class Queue(framework.Queue):
+    _queue: usim.Queue[bytes]
+
+    def __init__(self):
+        super().__init__()
+        self._queue = usim.Queue()
+
+    async def put(self, data: bytes) -> None:
+        await self._queue.put(data)
+
+    async def get(self) -> bytes:
+        return await self._queue
+
+    def empty(self) -> bool:
+        return len(self._queue._buffer) == 0
diff --git a/mixnet/node.py b/mixnet/node.py
index b4949f0..a2e110c 100644
--- a/mixnet/node.py
+++ b/mixnet/node.py
@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import asyncio
 import hashlib
 from enum import Enum
 from typing import Awaitable, Callable, TypeAlias
@@ -14,28 +13,33 @@ from pysphinx.sphinx import (
 )
 
 from mixnet.config import GlobalConfig, NodeConfig
-from mixnet.connection import LocalSimplexConnection, SimplexConnection
+from mixnet.connection import SimplexConnection
+from mixnet.framework.framework import Framework, Queue
 from mixnet.packet import Fragment, MessageFlag, MessageReconstructor, PacketBuilder
 
-NetworkPacketQueue: TypeAlias = asyncio.Queue[bytes]
-BroadcastChannel: TypeAlias = asyncio.Queue[bytes]
+NetworkPacketQueue: TypeAlias = Queue
+BroadcastChannel: TypeAlias = Queue
 
 
 class Node:
+    framework: Framework
     config: NodeConfig
     global_config: GlobalConfig
     mixgossip_channel: MixGossipChannel
     reconstructor: MessageReconstructor
     broadcast_channel: BroadcastChannel
 
-    def __init__(self, config: NodeConfig, global_config: GlobalConfig):
+    def __init__(
+        self, framework: Framework, config: NodeConfig, global_config: GlobalConfig
+    ):
+        self.framework = framework
         self.config = config
         self.global_config = global_config
         self.mixgossip_channel = MixGossipChannel(
-            config.peering_degree, self.__process_sphinx_packet
+            framework, config.peering_degree, self.__process_sphinx_packet
         )
         self.reconstructor = MessageReconstructor()
-        self.broadcast_channel = asyncio.Queue()
+        self.broadcast_channel = framework.queue()
 
     async def __process_sphinx_packet(
         self, packet: SphinxPacket
@@ -64,14 +68,16 @@ class Node:
     def connect(
         self,
         peer: Node,
-        inbound_conn: SimplexConnection = LocalSimplexConnection(),
-        outbound_conn: SimplexConnection = LocalSimplexConnection(),
+        inbound_conn: SimplexConnection,
+        outbound_conn: SimplexConnection,
     ):
         self.mixgossip_channel.add_conn(
             DuplexConnection(
                 inbound_conn,
                 MixSimplexConnection(
-                    outbound_conn, self.global_config.transmission_rate_per_sec
+                    self.framework,
+                    outbound_conn,
+                    self.global_config.transmission_rate_per_sec,
                 ),
             )
         )
@@ -79,7 +85,9 @@ class Node:
             DuplexConnection(
                 outbound_conn,
                 MixSimplexConnection(
-                    inbound_conn, self.global_config.transmission_rate_per_sec
+                    self.framework,
+                    inbound_conn,
+                    self.global_config.transmission_rate_per_sec,
                 ),
             )
         )
@@ -93,6 +101,7 @@ class Node:
 
 
 class MixGossipChannel:
+    framework: Framework
     peering_degree: int
     conns: list[DuplexConnection]
     handler: Callable[[SphinxPacket], Awaitable[SphinxPacket | None]]
@@ -100,9 +109,11 @@ class MixGossipChannel:
 
     def __init__(
         self,
+        framework: Framework,
         peering_degree: int,
         handler: Callable[[SphinxPacket], Awaitable[SphinxPacket | None]],
     ):
+        self.framework = framework
         self.peering_degree = peering_degree
         self.conns = []
         self.handler = handler
@@ -117,10 +128,8 @@ class MixGossipChannel:
             raise ValueError("The peering degree is reached.")
 
         self.conns.append(conn)
-        task = asyncio.create_task(self.__process_inbound_conn(conn))
+        task = self.framework.spawn(self.__process_inbound_conn(conn))
         self.tasks.add(task)
-        # To discard the task from the set automatically when it is done.
-        task.add_done_callback(self.tasks.discard)
 
     async def __process_inbound_conn(self, conn: DuplexConnection):
         while True:
@@ -166,24 +175,31 @@ class DuplexConnection:
 
 
 class MixSimplexConnection:
+    framework: Framework
     queue: NetworkPacketQueue
     conn: SimplexConnection
     transmission_rate_per_sec: float
 
-    def __init__(self, conn: SimplexConnection, transmission_rate_per_sec: float):
-        self.queue = asyncio.Queue()
+    def __init__(
+        self,
+        framework: Framework,
+        conn: SimplexConnection,
+        transmission_rate_per_sec: float,
+    ):
+        self.framework = framework
+        self.queue = framework.queue()
         self.conn = conn
         self.transmission_rate_per_sec = transmission_rate_per_sec
-        self.task = asyncio.create_task(self.__run())
+        self.task = framework.spawn(self.__run())
 
     async def __run(self):
         while True:
-            await asyncio.sleep(1 / self.transmission_rate_per_sec)
+            await self.framework.sleep(1 / self.transmission_rate_per_sec)
             # TODO: time mixing
             if self.queue.empty():
                 elem = build_noise_packet()
             else:
-                elem = self.queue.get_nowait()
+                elem = await self.queue.get()
             await self.conn.send(elem)
 
     async def send(self, elem: bytes):
diff --git a/mixnet/sim/config.py b/mixnet/sim/config.py
index 0de0ee0..bdffb7a 100644
--- a/mixnet/sim/config.py
+++ b/mixnet/sim/config.py
@@ -31,27 +31,13 @@ class Config:
 
 @dataclass
 class SimulationConfig:
-    time_scale: float
     duration_sec: int
     net_latency_sec: float
 
     def validate(self):
-        assert self.time_scale > 0
         assert self.duration_sec > 0
         assert self.net_latency_sec > 0
 
-    def scale_time(self, time: float) -> float:
-        return time * self.time_scale
-
-    def scale_rate(self, rate: int) -> float:
-        return float(rate / self.time_scale)
-
-    def scaled_duration(self) -> float:
-        return self.scale_time(self.duration_sec)
-
-    def scaled_net_latency(self) -> float:
-        return self.scale_time(self.net_latency_sec)
-
 
 @dataclass
 class LogicConfig:
diff --git a/mixnet/sim/config.yaml b/mixnet/sim/config.yaml
index cd92751..f605b42 100644
--- a/mixnet/sim/config.yaml
+++ b/mixnet/sim/config.yaml
@@ -1,6 +1,5 @@
 simulation:
-  time_scale: 0.001
-  duration_sec: 10000
+  duration_sec: 1000
   net_latency_sec: 0.01
 
 logic:
diff --git a/mixnet/sim/connection.py b/mixnet/sim/connection.py
index dfaf1e9..36db151 100644
--- a/mixnet/sim/connection.py
+++ b/mixnet/sim/connection.py
@@ -1,32 +1,34 @@
-import asyncio
 import math
-import time
+from typing import Awaitable
 
 import pandas
 
 from mixnet.connection import SimplexConnection
+from mixnet.framework.framework import Framework, Queue
 from mixnet.sim.config import SimulationConfig
 
 
 class MeteredRemoteSimplexConnection(SimplexConnection):
+    framework: Framework
     config: SimulationConfig
-    outputs: asyncio.Queue
-    conn: asyncio.Queue
-    inputs: asyncio.Queue
-    output_task: asyncio.Task
+    outputs: Queue
+    conn: Queue
+    inputs: Queue
+    output_task: Awaitable
     output_meters: list[int]
-    input_task: asyncio.Task
+    input_task: Awaitable
     input_meters: list[int]
 
-    def __init__(self, config: SimulationConfig):
+    def __init__(self, config: SimulationConfig, framework: Framework):
+        self.framework = framework
         self.config = config
-        self.outputs = asyncio.Queue()
-        self.conn = asyncio.Queue()
-        self.inputs = asyncio.Queue()
+        self.outputs = framework.queue()
+        self.conn = framework.queue()
+        self.inputs = framework.queue()
         self.output_meters = []
-        self.output_task = asyncio.create_task(self.__run_output_task())
+        self.output_task = framework.spawn(self.__run_output_task())
         self.input_meters = []
-        self.input_task = asyncio.create_task(self.__run_input_task())
+        self.input_task = framework.spawn(self.__run_input_task())
 
     async def send(self, data: bytes) -> None:
         await self.outputs.put(data)
@@ -35,22 +37,24 @@ class MeteredRemoteSimplexConnection(SimplexConnection):
         return await self.inputs.get()
 
     async def __run_output_task(self):
-        start_time = time.time()
+        start_time = self.framework.now()
         while True:
             data = await self.outputs.get()
             self.__update_meter(self.output_meters, len(data), start_time)
             await self.conn.put(data)
 
     async def __run_input_task(self):
-        start_time = time.time()
+        start_time = self.framework.now()
         while True:
-            await asyncio.sleep(self.config.scaled_net_latency())
             data = await self.conn.get()
+            if data is None:
+                break
+            await self.framework.sleep(self.config.net_latency_sec)
             self.__update_meter(self.input_meters, len(data), start_time)
             await self.inputs.put(data)
 
     def __update_meter(self, meters: list[int], size: int, start_time: float):
-        slot = math.floor((time.time() - start_time) / self.config.time_scale)
+        slot = math.floor(self.framework.now() - start_time)
         assert slot >= len(meters) - 1
         meters.extend([0] * (slot - len(meters) + 1))
         meters[-1] += size
diff --git a/mixnet/sim/main.py b/mixnet/sim/main.py
index 11389d5..9a9b0cd 100644
--- a/mixnet/sim/main.py
+++ b/mixnet/sim/main.py
@@ -1,5 +1,6 @@
 import argparse
-import asyncio
+
+import usim
 
 from mixnet.sim.config import Config
 from mixnet.sim.simulation import Simulation
@@ -16,6 +17,6 @@ if __name__ == "__main__":
 
     config = Config.load(args.config)
     sim = Simulation(config)
-    asyncio.run(sim.run())
+    usim.run(sim.run())
 
     print("Simulation complete!")
diff --git a/mixnet/sim/simulation.py b/mixnet/sim/simulation.py
index a7d504a..38fde6b 100644
--- a/mixnet/sim/simulation.py
+++ b/mixnet/sim/simulation.py
@@ -1,8 +1,10 @@
-import asyncio
 import random
-import time
 
+import usim
+
+import mixnet.framework.usim as usimfw
 from mixnet.config import GlobalConfig, MixMembership, NodeInfo
+from mixnet.framework.framework import Framework
 from mixnet.node import Node
 from mixnet.sim.config import Config
 from mixnet.sim.connection import MeteredRemoteSimplexConnection
@@ -10,20 +12,25 @@ from mixnet.sim.stats import ConnectionStats
 
 
 class Simulation:
+    config: Config
+    framework: Framework
+
     def __init__(self, config: Config):
         random.seed()
         self.config = config
 
     async def run(self):
-        nodes, conn_measurement = self.init_nodes()
+        conn_stats = await self._run()
+        conn_stats.bandwidths()
 
-        deadline = time.time() + self.config.simulation.scaled_duration()
-        tasks: list[asyncio.Task] = []
-        for node in nodes:
-            tasks.append(asyncio.create_task(self.run_logic(node, deadline)))
-        await asyncio.gather(*tasks)
-
-        conn_measurement.bandwidths()
+    async def _run(self) -> ConnectionStats:
+        async with usim.until(usim.time + self.config.simulation.duration_sec) as scope:
+            self.framework = usimfw.Framework(scope)
+            nodes, conn_stats = self.init_nodes()
+            for node in nodes:
+                self.framework.spawn(self.run_logic(node))
+            return conn_stats
+        assert False  # unreachable
 
     def init_nodes(self) -> tuple[list[Node], ConnectionStats]:
         node_configs = self.config.mixnet.node_configs()
@@ -34,16 +41,20 @@ class Simulation:
                     for node_config in node_configs
                 ]
             ),
-            self.config.simulation.scale_rate(
-                self.config.mixnet.transmission_rate_per_sec
-            ),
+            self.config.mixnet.transmission_rate_per_sec,
             self.config.mixnet.max_mix_path_length,
         )
-        nodes = [Node(node_config, global_config) for node_config in node_configs]
+        nodes = [
+            Node(self.framework, node_config, global_config)
+            for node_config in node_configs
+        ]
 
         conn_stats = ConnectionStats()
         for i, node in enumerate(nodes):
-            inbound_conn, outbound_conn = self.create_conn(), self.create_conn()
+            inbound_conn, outbound_conn = (
+                self.create_conn(),
+                self.create_conn(),
+            )
             peer = nodes[(i + 1) % len(nodes)]
             node.connect(peer, inbound_conn, outbound_conn)
             conn_stats.register(node, inbound_conn, outbound_conn)
@@ -52,15 +63,10 @@ class Simulation:
         return nodes, conn_stats
 
     def create_conn(self) -> MeteredRemoteSimplexConnection:
-        return MeteredRemoteSimplexConnection(self.config.simulation)
-
-    async def run_logic(self, node: Node, deadline: float):
-        while time.time() < deadline:
-            await asyncio.sleep(
-                self.config.simulation.scale_time(
-                    self.config.logic.lottery_interval_sec
-                )
-            )
+        return MeteredRemoteSimplexConnection(self.config.simulation, self.framework)
 
+    async def run_logic(self, node: Node):
+        while True:
+            await (usim.time + self.config.logic.lottery_interval_sec)
             if random.random() < self.config.logic.sender_prob:
                 await node.send_message(b"selected block")
diff --git a/mixnet/test_node.py b/mixnet/test_node.py
index f4ba644..bd62c2e 100644
--- a/mixnet/test_node.py
+++ b/mixnet/test_node.py
@@ -1,6 +1,8 @@
 import asyncio
 from unittest import IsolatedAsyncioTestCase
 
+import mixnet.framework.asyncio as asynciofw
+from mixnet.connection import LocalSimplexConnection
 from mixnet.node import Node
 from mixnet.test_utils import (
     init_mixnet_config,
@@ -9,13 +11,17 @@ from mixnet.test_utils import (
 
 class TestNode(IsolatedAsyncioTestCase):
     async def test_node(self):
+        framework = asynciofw.Framework()
         global_config, node_configs, _ = init_mixnet_config(10)
-        nodes = [Node(node_config, global_config) for node_config in node_configs]
+        nodes = [
+            Node(framework, node_config, global_config) for node_config in node_configs
+        ]
         for i, node in enumerate(nodes):
-            try:
-                node.connect(nodes[(i + 1) % len(nodes)])
-            except ValueError as e:
-                print(e)
+            node.connect(
+                nodes[(i + 1) % len(nodes)],
+                LocalSimplexConnection(framework),
+                LocalSimplexConnection(framework),
+            )
 
         await nodes[0].send_message(b"block selection")
 
@@ -24,7 +30,7 @@ class TestNode(IsolatedAsyncioTestCase):
             broadcasted_msgs = []
             for node in nodes:
                 if not node.broadcast_channel.empty():
-                    broadcasted_msgs.append(node.broadcast_channel.get_nowait())
+                    broadcasted_msgs.append(await node.broadcast_channel.get())
 
             if len(broadcasted_msgs) == 0:
                 await asyncio.sleep(1)
diff --git a/requirements.txt b/requirements.txt
index d89ad06..f6462eb 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,4 +6,4 @@ pycparser==2.21
 pysphinx==0.0.3
 scipy==1.11.4
 black==23.12.1
-sympy==1.12
+usim==0.4.4